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Sample records for aerosol absorption properties

  1. Identifying Aerosol Type/Mixture from Aerosol Absorption Properties Using AERONET

    NASA Technical Reports Server (NTRS)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Dickerson, R. R.; Thompson, A. M.; Slutsker, I.; Li, Z.; Tripathi, S. N.; Singh, R. P.; Zibordi, G.

    2010-01-01

    Aerosols are generated in the atmosphere through anthropogenic and natural mechanisms. These sources have signatures in the aerosol optical and microphysical properties that can be used to identify the aerosol type/mixture. Spectral aerosol absorption information (absorption Angstrom exponent; AAE) used in conjunction with the particle size parameterization (extinction Angstrom exponent; EAE) can only identify the dominant absorbing aerosol type in the sample volume (e.g., black carbon vs. iron oxides in dust). This AAE/EAE relationship can be expanded to also identify non-absorbing aerosol types/mixtures by applying an absorption weighting. This new relationship provides improved aerosol type distinction when the magnitude of absorption is not equal (e.g, black carbon vs. sulfates). The Aerosol Robotic Network (AERONET) data provide spectral aerosol optical depth and single scattering albedo - key parameters used to determine EAE and AAE. The proposed aerosol type/mixture relationship is demonstrated using the long-term data archive acquired at AERONET sites within various source regions. The preliminary analysis has found that dust, sulfate, organic carbon, and black carbon aerosol types/mixtures can be determined from this AAE/EAE relationship when applying the absorption weighting for each available wavelength (Le., 440, 675, 870nm). Large, non-spherical dust particles absorb in the shorter wavelengths and the application of 440nm wavelength absorption weighting produced the best particle type definition. Sulfate particles scatter light efficiently and organic carbon particles are small near the source and aggregate over time to form larger less absorbing particles. Both sulfates and organic carbon showed generally better definition using the 870nm wavelength absorption weighting. Black carbon generation results from varying combustion rates from a number of sources including industrial processes and biomass burning. Cases with primarily black carbon showed

  2. Remote sensing of ocean color and aerosol properties: resolving the issue of aerosol absorption.

    PubMed

    Gordon, H R; Du, T; Zhang, T

    1997-11-20

    Current atmospheric correction and aerosol retrieval algorithms for ocean color sensors use measurements of the top-of-the-atmosphere reflectance in the near infrared, where the contribution from the ocean is known for case 1 waters, to assess the aerosol optical properties. Such measurements are incapable of distinguishing between weakly and strongly absorbing aerosols, and the atmospheric correction and aerosol retrieval algorithms fail if the incorrect absorption properties of the aerosol are assumed. We present an algorithm that appears promising for the retrieval of in-water biophysical properties and aerosol optical properties in atmospheres containing both weakly and strongly absorbing aerosols. By using the entire spectrum available to most ocean color instruments (412-865 nm), we simultaneously recover the ocean's bio-optical properties and a set of aerosol models that best describes the aerosol optical properties. The algorithm is applied to simulated situations that are likely to occur off the U.S. East Coast in summer when the aerosols could be of the locally generated weakly absorbing Maritime type or of the pollution-generated strongly absorbing urban-type transported over the ocean by the winds. The simulations show that the algorithm behaves well in an atmosphere with either weakly or strongly absorbing aerosol. The algorithm successfully identifies absorbing aerosols and provides close values for the aerosol optical thickness. It also provides excellent retrievals of the ocean bio-optical properties. The algorithm uses a bio-optical model of case 1 waters and a set of aerosol models for its operation. The relevant parameters of both the ocean and atmosphere are systematically varied to find the best (in a rms sense) fit to the measured top-of-the-atmosphere spectral reflectance. Examples are provided that show the algorithm's performance in the presence of errors, e.g., error in the contribution from whitecaps and error in radiometric calibration.

  3. Characterization of Spectral Absorption Properties of Aerosols Using Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, O.; Jethva, H.; Bhartia, P. K.; Ahn, C.

    2012-01-01

    The wavelength-dependence of aerosol absorption optical depth (AAOD) is generally represented in terms of the Angstrom Absorption Exponent (AAE), a parameter that describes the dependence of AAOD with wavelength. The AAE parameter is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses high spectral resolution measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measured reflectance (rho lambda) is approximately given by Beer's law rho lambda = rho (sub 0 lambda) e (exp -mtau (sub abs lambda)) where rho(sub 0 lambda) is the cloud reflectance, m is the geometric slant path and tau (sub abs lambda) is the spectral AAOD. The rho (sub 0 lambda) term is determined by means of radiative transfer calculations using as input the cloud optical depth derived as described in Torres et al. [JAS, 2012] that accounts for the effects of aerosol absorption. In the second step, corrections for molecular and aerosol scattering effects are applied to the cloud reflectance term, and the spectral AAOD is then derived by inverting the equation above. The proposed technique will be discussed in detail and application results will be presented. The technique can be easily applied to hyper-spectral satellite measurements that include UV such as OMI, GOME and SCIAMACHY, or to multi-spectral visible measurements by other sensors provided that the aerosol-above-cloud events are easily identified.

  4. Retrieval of Aerosol Absorption Properties from Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, Omar; Bhartia, Pawan K.; Jethva, H.; Ahn, Chang-Woo

    2012-01-01

    The Angstrom Absorption Exponent (AAE) is a parameter commonly used to characterize the wavelength-dependence of aerosol absorption optical depth (AAOD). It is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses multi-spectral measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measurement can be explained, using an approximations of Beer's Law (BL), as the upwelling reflectance at the cloud top attenuated by the absorption effects of the overlying aerosol layer. The upwelling reflectance at the cloud-top in an aerosol-free atmospheric column is mainly a function of cloud optical depth (COD). In the proposed method of AAE derivation, the first step is determining COD which is retrieved using a previously developed color-ratio based approach. In the second step, corrections for molecular scattering effects are applied to both the observed ad the calculated cloud reflectance terms, and the spectral AAOD is then derived by an inversion of the BL approximation. The proposed technique will be discussed in detail and application results making use of OMI multi-spectral measurements in the UV-Vis. will be presented.

  5. Organic Aerosols from SÃO Paulo and its Relationship with Aerosol Absorption and Scattering Properties

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Brito, J. F.; Rizzo, L. V.

    2012-12-01

    The megacity of São Paulo with its 19 million people and 7 million cars is a challenge from the point of view of air pollution. High levels of organic aerosols, PM10, black carbon and ozone and the peculiar situation of the large scale use of ethanol fuel makes it a special case. Little is known about the impact of ethanol on air quality and human health and the increase of ethanol as vehicle fuel is rising worldwide An experiment was designed to physico-chemical properties of aerosols in São Paulo, as well as their optical properties. Aerosol size distribution in the size range of 1nm to 10 micrometers is being measured with a Helsinki University SMPS (Scanning Mobility Particle Sizer), an NAIS (Neutral ion Spectrometer) and a GRIMM OPC (Optical Particle Counter). Optical properties are being measured with a TSI Nephelometer and a Thermo MAAP (Multi Angle Absorption Photometer). A CIMEL sunphotometer from the AERONET network measure the aerosol optical depth. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to real-time VOC analysis and aerosol composition, respectively. The ACSM was operated for 3 months continuosly during teh wintertime of 2012. The measured total particle concentration typically varies between 10,000 and 30,000 cm-3 being the lowest late in the night and highest around noon and frequently exceeding 50,000 cm-3. Clear diurnal patterns in aerosol optical properties were observed. Scattering and absorption coefficients typically range between 20 and 100 Mm-1 at 450 nm, and between 10 to 40 Mm-1 at 637 nm, respectively, both of them peaking at 7:00 local time, the morning rush hour. The corresponding single scattering albedo varies between 0.50 and 0.85, indicating a significant contribution of primary absorbing particles to the aerosol population. During the first month a total of seven new particle formation events were observed with growth rates ranging from 9 to 25

  6. Radiative properties of the background aerosol: absorption component of extinction.

    PubMed

    Clarke, A D; Charlson, R J

    1985-07-19

    The light-scattering and light-absorption coefficients of the global background aerosol define its single-scatter albedo. Continuous, simultaneous measurements of these optical coefficients were made on a daily basis for the remote marine mid-troposphere; such measurements are essential for assessment of the effects of aerosol on atmospheric radiative transfer. Measurements of light-absorption coefficients made at the Mauna Loa Observatory in Hawaii were higher than expected, and the single-scatter albedo was lower than the value often used in radiative transfer models. Soot appears to be the most likely primary absorber, and hemispheric dispersal of this combustion-derived material is suggested.

  7. An Analysis of AERONET Aerosol Absorption Properties and Classifications Representative of Aerosol Source Regions

    NASA Technical Reports Server (NTRS)

    Giles, David M.; Holben, Brent N.; Eck, Thomas F.; Sinyuk, Aliaksandr; Smirnov, Alexander; Slutsker, Ilya; Dickerson, R. R.; Thompson, A. M.; Schafer, J. S.

    2012-01-01

    Partitioning of mineral dust, pollution, smoke, and mixtures using remote sensing techniques can help improve accuracy of satellite retrievals and assessments of the aerosol radiative impact on climate. Spectral aerosol optical depth (tau) and single scattering albedo (omega (sub 0) ) from Aerosol Robotic Network (AERONET) measurements are used to form absorption [i.e., omega (sub 0) and absorption Angstrom exponent (alpha(sub abs))] and size [i.e., extinction Angstrom exponent (alpha(sub ext)) and fine mode fraction of tau] relationships to infer dominant aerosol types. Using the long-term AERONET data set (1999-2010), 19 sites are grouped by aerosol type based on known source regions to: (1) determine the average omega (sub 0) and alpha(sub abs) at each site (expanding upon previous work); (2) perform a sensitivity study on alpha(sub abs) by varying the spectral omega (sub 0); and (3) test the ability of each absorption and size relationship to distinguish aerosol types. The spectral omega (sub 0) averages indicate slightly more aerosol absorption (i.e., a 0.0 < delta omega (sub 0) <= 0.02 decrease) than in previous work and optical mixtures of pollution and smoke with dust show stronger absorption than dust alone. Frequency distributions of alpha(sub abs) show significant overlap among aerosol type categories and at least 10% of the alpha(sub abs) retrievals in each category are below 1.0. Perturbing the spectral omega (sub 0) by +/- 0.03 induces significant alpha(sub abs) changes from the unperturbed value by at least approx. +/- 0.6 for Dust, approx. +/-0.2 for Mixed, and approx. +/-0.1 for Urban/Industrial and Biomass Burning. The omega (sub 0)440nm and alpha(sub ext) 440-870nm relationship shows the best separation among aerosol type clusters, providing a simple technique for determining aerosol type from surface- and future space-based instrumentation.

  8. An analysis of AERONET aerosol absorption properties and classifications representative of aerosol source regions

    NASA Astrophysics Data System (ADS)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Smirnov, A.; Slutsker, I.; Dickerson, R. R.; Thompson, A. M.; Schafer, J. S.

    2012-09-01

    Partitioning of mineral dust, pollution, smoke, and mixtures using remote sensing techniques can help improve accuracy of satellite retrievals and assessments of the aerosol radiative impact on climate. Spectral aerosol optical depth (τ) and single scattering albedo (ωo) from Aerosol Robotic Network (AERONET) measurements are used to form absorption (i.e., ωo and absorption Ångström exponent (αabs)) and size (i.e., extinction Ångström exponent (αext) and fine mode fraction of τ) relationships to infer dominant aerosol types. Using the long-term AERONET data set (1999-2010), 19 sites are grouped by aerosol type based on known source regions to (1) determine the averageωo and αabs at each site (expanding upon previous work), (2) perform a sensitivity study on αabs by varying the spectral ωo, and (3) test the ability of each absorption and size relationship to distinguish aerosol types. The spectral ωo averages indicate slightly more aerosol absorption (i.e., a 0.0 < δωo ≤ 0.02 decrease) than in previous work, and optical mixtures of pollution and smoke with dust show stronger absorption than dust alone. Frequency distributions of αabs show significant overlap among aerosol type categories, and at least 10% of the αabs retrievals in each category are below 1.0. Perturbing the spectral ωo by ±0.03 induces significant αabs changes from the unperturbed value by at least ˜±0.6 for Dust, ˜±0.2 for Mixed, and ˜±0.1 for Urban/Industrial and Biomass Burning. The ωo440nm and αext440-870nmrelationship shows the best separation among aerosol type clusters, providing a simple technique for determining aerosol type from surface- and future space-based instrumentation.

  9. Light absorption properties and radiative effects of primary organic aerosol emissions.

    PubMed

    Lu, Zifeng; Streets, David G; Winijkul, Ekbordin; Yan, Fang; Chen, Yanju; Bond, Tami C; Feng, Yan; Dubey, Manvendra K; Liu, Shang; Pinto, Joseph P; Carmichael, Gregory R

    2015-04-21

    Organic aerosols (OAs) in the atmosphere affect Earth's energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called "brown carbon" (BrC) component. However, the absorptivities of OAs are not represented or are poorly represented in current climate and chemical transport models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle's absorptivity) and their uncertainties for the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parametrize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, indicating that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory, and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ∼27% reduction in the amount of the net global average POA cooling compared to results from the nonabsorbing assumption.

  10. Measurements of scattering and absorption properties of surface aerosols at a semi-arid site, Anantapur

    NASA Astrophysics Data System (ADS)

    Rama Gopal, K.; Balakrishnaiah, G.; Arafath, S. Md.; Raja Obul Reddy, K.; Siva Kumar Reddy, N.; Pavan Kumari, S.; Raghavendra Kumar, K.; Chakradhar Rao, T.; Lokeswara Reddy, T.; Reddy, R. R.; Nazeer Hussain, S.; Vasudeva Reddy, M.; Suresh Babu, S.; Mallikarjuna Reddy, P.

    2017-01-01

    Aerosol optical properties are continuously measured at a semi-arid station, Anantapur from June 2012 to May 2013 which describes the impact of surface aerosols on climate change over the region. Scattering coefficient (σsct) and absorption coefficient (σabs) are obtained from integrating Nephelometer and Aethalometer, respectively. Also, the single scattering albedo (ω0), Scattering/absorption Ångström exponents were examined during the period of study. Diurnal variations of σsct and σabs show a bi-peak pattern with two maxima and one minimum in a day. The largest values of σsct and σabs are obtained in winter while the lowest values are measured in monsoon. From the measurements σsct550 and σabs550 are found to be 110 ± 12.23 Mm- 1 and 33 ± 5.2 Mm- 1, respectively during the study period. An analysis of the ω0 suggests that there is a more absorbing fraction in the particle composition over the measurement site. The ω0 obtained in the surface boundary layer of Anantapur is below the critical value of 0.86 that determines the shift from cooling to warming. A relationship between scattering/absorption coefficients and scattering/absorption Ångström exponent and single scattering albedo is further examined. In order to understand the origins of the air masses in the study region, we performed seven-day back trajectory analyses based on the NOAA HYSPLIT model. These trajectories were computed at several altitudes (3000 m, 1500 m, and 500 m) for June 2012 and May 2013. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosol only.

  11. Analysis of aerosol absorption properties and transport over North Africa and the Middle East using AERONET data

    NASA Astrophysics Data System (ADS)

    Farahat, Ashraf; El-Askary, Hesham; Adetokunbo, Peter; Fuad, Abu-Tharr

    2016-11-01

    In this paper particle categorization and absorption properties were discussed to understand transport mechanisms at different geographic locations and possible radiative impacts on climate. The long-term Aerosol Robotic Network (AERONET) data set (1999-2015) is used to estimate aerosol optical depth (AOD), single scattering albedo (SSA), and the absorption Ångström exponent (αabs) at eight locations in North Africa and the Middle East. Average variation in SSA is calculated at four wavelengths (440, 675, 870, and 1020 nm), and the relationship between aerosol absorption and physical properties is used to infer dominant aerosol types at different locations. It was found that seasonality and geographic location play a major role in identifying dominant aerosol types at each location. Analyzing aerosol characteristics among different sites using AERONET Version 2, Level 2.0 data retrievals and the Hybrid Single Particle Lagrangian Integrated Trajectory model (HYSPLIT) backward trajectories shows possible aerosol particle transport among different locations indicating the importance of understanding transport mechanisms in identifying aerosol sources.

  12. Aerosol Scattering and Absorption Properties Over the Central Himalayan Location Nainital: Results from Gvax

    NASA Astrophysics Data System (ADS)

    Gogoi, M. M.; Babu, S.; Nair, V. S.; Satheesh, S.; Naja, M.; Kotamarthi, V. R.

    2012-12-01

    Extensive characterization of aerosols over a central Himalayan location, Nainital (29.4° N, 79.5° E, 1958 m amsl) were carried out during June 2011 to March 2012 under the Ganges Valley Aerosol Experiment (GVAX). Owing to the highly turbid, persistent and increasing aerosol concentration over the Ganges Valley in northern India, their influence on surface dimming, mid-tropospheric warming and monsoon circulations, the experimental site Nainital is best suited for studying the regional distribution of complex aerosol sources, their transport and direct and indirect radiative forcing mechanisms. During the study period, aerosol scattering (absorption) coefficients showed values as high as > 500 Mm-1 (> 50 Mm-1) in local noon time during the onset of winter and early spring and as low as < 300 Mm-1 (< 40 Mm-1) during the summer months. Consequently, aerosol single scattering albedo (SSA) decreased in winter (< 0.9, for 45% of occurrences) with large day-to-day modulations and higher values (> 0.9, for 81% of occurrences) during summer. Based on the spectral distribution of scattering coefficients, fine mode aerosols dominate the summer compared to winter season. The strong absorption during the winter and early spring is associated with the prevalence of biomass burning aerosols and/or dust as reveal by the steep spectral dependence of absorption coefficients (αabs >2.0). These observed seasonal variations are attributed to the dynamics of the atmospheric boundary layer as well as the influence of long range transport over the Himalayan location.

  13. Optical Absorption Characteristics of Aerosols.

    DTIC Science & Technology

    1985-09-11

    properties of the powder as well as the thickness of the layer. For a layer that is thick enough so that no light is transmitted, the Kubelka -- Munk theory...which is a two stream radiative transfer model, relates the reflectance to the ratio of the absorption to the scattering. The Kubelka - Munk theory has...of the aerosol material is known. Under the assumptions of the Kubelka - Munk . theory, the imaginary component of the refractive index is deter- mined

  14. Remote Sensing of Aerosol and Non-Aerosol Absorption

    NASA Technical Reports Server (NTRS)

    Kaufman, Y. J.; Dubovik, O.; Holben, B. N.; Remer, L. A.; Tanre, D.; Lau, William K. M. (Technical Monitor)

    2001-01-01

    Remote sensing of aerosol from the new satellite instruments (e.g. MODIS from Terra) and ground based radiometers (e.g. the AERONET) provides the opportunity to measure the absorption characteristics of the ambient undisturbed aerosol in the entire atmospheric column. For example Landsat and AERONET data are used to measure spectral absorption of sunlight by dust from West Africa. Both Application of the Landsat and AERONET data demonstrate that Saharan dust absorption of solar radiation is several times smaller than the current international standards. This is due to difficulties of measuring dust absorption in situ, and due to the often contamination of dust properties by the presence of air pollution or smoke. We use the remotely sensed aerosol absorption properties described by the spectral sin le scattering albedo, together with statistics of the monthly optical thickness for the fine and coarse aerosol derived from the MODIS data. The result is an estimate of the flux of solar radiation absorbed by the aerosol layer in different regions around the globe where aerosol is prevalent. If this aerosol forcing through absorption is not included in global circulation models, it may be interpreted as anomalous absorption in these regions. In a preliminary exercise we also use the absorption measurements by AERONET, to derive the non-aerosol absorption of the atmosphere in cloud free conditions. The results are obtained for the atmospheric windows: 0.44 microns, 0.66 microns, 0.86 microns and 1.05 microns. In all the locations over the land and ocean that were tested no anomalous absorption in these wavelengths, was found within absorption optical thickness of +/- 0.005.

  15. Light Absorption Properties and Radiative Effects of Primary Organic Aerosol Emissions

    EPA Science Inventory

    Organic aerosols (OA) in the atmosphere affect Earth’s energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called “brown carbon” (BrC) component. However, the absorptivities of OA are not or poorly represented in current climate m...

  16. Absorption Properties of Mediterranean Aerosols Obtained from Multi-year Ground-based and Satellite Remote Sensing Observations

    NASA Technical Reports Server (NTRS)

    Mallet, M.; Dubovik, O.; Nabat, P.; Dulac, F.; Kahn, R.; Sciare, J.; Paronis, D.; Leon, J. F.

    2013-01-01

    Aerosol absorption properties are of high importance to assess aerosol impact on regional climate. This study presents an analysis of aerosol absorption products obtained over the Mediterranean Basin or land stations in the region from multi-year ground-based AERONET and satellite observations with a focus on the Absorbing Aerosol Optical Depth (AAOD), Single Scattering Albedo (SSA) and their spectral dependence. The AAOD and Absorption Angstrom Exponent (AAE) data set is composed of daily averaged AERONET level 2 data from a total of 22 Mediterranean stations having long time series, mainly under the influence of urban-industrial aerosols and/or soil dust. This data set covers the 17 yr period 1996-2012 with most data being from 2003-2011 (approximately 89 percent of level-2 AAOD data). Since AERONET level-2 absorption products require a high aerosol load (AOD at 440 nm greater than 0.4), which is most often related to the presence of desert dust, we also consider level-1.5 SSA data, despite their higher uncertainty, and filter out data with an Angstrom exponent less than 1.0 in order to study absorption by carbonaceous aerosols. The SSA data set includes both AERONET level-2 and satellite level-3 products. Satellite-derived SSA data considered are monthly level 3 products mapped at the regional scale for the spring and summer seasons that exhibit the largest aerosol loads. The satellite SSA dataset includes the following products: (i) Multi-angle Imaging SpectroRadiometer (MISR) over 2000-2011, (ii) Ozone Monitoring Instrument (OMI) near-UV algorithm over 2004-2010, and (iii) MODerate resolution Imaging Spectroradiometer (MODIS) Deep-Blue algorithm over 2005-2011, derived only over land in dusty conditions. Sun-photometer observations show that values of AAOD at 440 nm vary between 0.024 +/- 0.01 (resp. 0.040 +/- 0.01) and 0.050 +/- 0.01 (0.055 +/- 0.01) for urban (dusty) sites. Analysis shows that the Mediterranean urban-industrial aerosols appear "moderately

  17. Light absorption, optical and microphysical properties of trajectory-clustered aerosols at two AERONET sites in West Africa

    NASA Astrophysics Data System (ADS)

    Fawole, O. G.; Cai, X.; MacKenzie, A. R.

    2015-12-01

    Aerosol remote sensing techniques and back-trajectory modeling can be combined to identify aerosol types. We have clustered 7 years of AERONET aerosol signals using trajectory analysis to identify dominant aerosol sources at two AERONET sites in West Africa: Ilorin (4.34 oE, 8.32 oN) and Djougou (1.60 oE, 9.76 oN). Of particular interest are air masses that have passed through the gas flaring region in the Niger Delta area, of Nigeria, en-route the AERONET sites. 7-day back trajectories were calculated using the UK UGAMP trajectory model driven by ECMWF wind analyses data. Dominant sources identified, using literature classifications, are desert dust (DD), Biomass burning (BB) and Urban-Industrial (UI). Below, we use a combination of synoptic trajectories and aerosol optical properties to distinguish a fourth source: that due to gas flaring. Gas flaring, (GF) the disposal of gas through stack in an open-air flame, is believed to be a prominent source of black carbon (BC) and greenhouse gases. For these different aerosol source signatures, single scattering albedo (SSA), refractive index , extinction Angstrom exponent (EEA) and absorption Angstrom exponent (AAE) were used to classify the light absorption characteristics of the aerosols for λ = 440, 675, 870 and1020 nm. A total of 1625 daily averages of aerosol data were collected for the two sites. Of which 245 make up the GF cluster for both sites. For GF cluster, the range of fine-mode fraction is 0.4 - 0.7. Average values SSA(λ), for the total and GF clusters are 0.90(440), 0.93(675), 0.95(870) and 0.96(1020), and 0.93(440), 0.92(675), 0.9(870) and 0.9(1020), respectively. Values of for the GF clusters for both sites are 0.62 - 1.11, compared to 1.28 - 1.66 for the remainder of the clusters, which strongly indicates the dominance of carbonaceous particles (BC), typical of a highly industrial area. An average value of 1.58 for the real part of the refractive index at low SSA for aerosol in the GF cluster is also

  18. Simulation model of absorption and scattering properties of laser light applied to urban aerosols over the city of Popayan, Colombia

    NASA Astrophysics Data System (ADS)

    Bastidas, Alvaro E.; Rodriguez, Edith; Jaramillo, Mauricio; Solarte, Efrain

    2004-11-01

    Aerosols are among the most spatially variable components of the atmosphere, and thus their study requires their monitoring over a broad geographic range. The backscattering of light from suspended solid and liquid particles in the atmosphere obeys Mie scattering theory. Light attenuation in the spectral region from 300 to 4000 nm due to Mie scattering exceeds that due to molecular (Rayleigh) scattering and ozone absorption combined. This occurs despite the fact that aerosol particle concentrations in the atmosphere are many orders of magnitude smaller than molecular concentrations. Starting from the characteristics of urban aerosols measured over the city of Popayan, Colombia), 2° 27" N; 76° 37' W, with a PM10 particle selector, we present the results of a study of light attenuation properties generated using Matlab computer code, to simulate and predict measurements with a Lidar system operating at 514.5 nm.

  19. Light Absorption Properties of Brown Carbon from Fresh and Aged Biomass Burning Aerosols Characterized in a Smog Chamber

    NASA Astrophysics Data System (ADS)

    Saleh, R.; Chuang, W.; Hennigan, C.; McMeeking, G. R.; Coe, H.; Donahue, N. M.; Robinson, A. L.

    2011-12-01

    Black carbon is an important particulate phase light absorber in the atmosphere. Recent studies have shown that some organic matter also absorb visible light, especially at short wavelengths. These organic compounds are referred to as "brown carbon". Biomass burning is a major contributor to brown carbon in atmospheric particulate matter; however, its optical properties are poorly characterized. We have conducted smog chamber experiments to investigate light absorption properties of brown carbon in primary and aged biomass burning emissions, namely the imaginary refractive index. The aging was performed in a smog chamber, where dilute emissions were exposed to UV lights to initiate photo-oxidation, which often produced substantial secondary organic aerosol. The experiments took place at Carnegie Mellon University (CMU) and at the US Fire Science Laboratory in Missoula, MT as part of the Fire Lab at Missoula field campaign (FLAME 2009). The CMU experiments simulated household wood burning (oak), and the FLAME experiments simulated wildland fires with fuels including gallberry, lodgepole pine, black spruce and ponderosa pine. Absorption coefficients were measured using an Aethalometer (Magee Scientific) at 7 different wavelengths ranging between 370 nm and 950 nm. The black carbon size distributions were measured using a Single Particle Soot Photometer (SP2, DMT), and total aerosol size distributions were measured using a Scanning Mobility Particle Sizer (SMPS, TSI). The absorption coefficients of both the fresh and aged aerosol were significantly larger, and had stronger wavelength dependence than what would be expected for black carbon alone, and for a black carbon core with a non-absorbing shell. This indicates that biomass burning organic aerosol should be classified as brown carbon. A (black carbon) core - (brown carbon) shell absorption model based on Mie theory was optimized to determine the shell imaginary refractive index which produces model outputs that

  20. Shortwave Radiative Fluxes, Solar-Beam Transmissions, and Aerosol Properties: TARFOX and ACE-2 Find More Absorption from Flux Radiometry than from Other Measurements

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Redemann, J.; Schmid, B.; Livingston, J. M.; Bergstrom, R. W.; Ramirez, S. A.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2) made simultaneous measurements of shortwave radiative fluxes, solar-beam transmissions, and the aerosols affecting those fluxes and transmissions. Besides the measured fluxes and transmissions, other obtained properties include aerosol scattering and absorption measured in situ at the surface and aloft; aerosol single scattering albedo retrieved from skylight radiances; and aerosol complex refractive index derived by combining profiles of backscatter, extinction, and size distribution. These measurements of North Atlantic boundary layer aerosols impacted by anthropogenic pollution revealed the following characteristic results: (1) Better agreement among different types of remote measurements of aerosols (e.g., optical depth, extinction, and backscattering from sunphotometers, satellites, and lidars) than between remote and in situ measurements; 2) More extinction derived from transmission measurements than from in situ measurements; (3) Larger aerosol absorption inferred from flux radiometry than from other measurements. When the measured relationships between downwelling flux and optical depth (or beam transmission) are used to derive best-fit single scattering albedos for the polluted boundary layer aerosol, both TARFOX and ACE-2 yield midvisible values of 0.90 +/- 0.04. The other techniques give larger single scattering albedos (i.e. less absorption) for the polluted boundary layer, with a typical result of 0.95 +/- 0.04. Although the flux-based results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., unknown gas absorption). Current uncertainties in aerosol single scattering albedo are large in terms of climate effects. They also have an important influence on aerosol optical depths retrieved from satellite radiances

  1. Aerosol Absorption Measurements in MILAGRO.

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

    2007-12-01

    During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due

  2. Aqueous aerosol SOA formation: impact on aerosol physical properties.

    PubMed

    Woo, Joseph L; Kim, Derek D; Schwier, Allison N; Li, Ruizhi; McNeill, V Faye

    2013-01-01

    Organic chemistry in aerosol water has recently been recognized as a potentially important source of secondary organic aerosol (SOA) material. This SOA material may be surface-active, therefore potentially affecting aerosol heterogeneous activity, ice nucleation, and CCN activity. Aqueous aerosol chemistry has also been shown to be a potential source of light-absorbing products ("brown carbon"). We present results on the formation of secondary organic aerosol material in aerosol water and the associated changes in aerosol physical properties from GAMMA (Gas-Aerosol Model for Mechanism Analysis), a photochemical box model with coupled gas and detailed aqueous aerosol chemistry. The detailed aerosol composition output from GAMMA was coupled with two recently developed modules for predicting a) aerosol surface tension and b) the UV-Vis absorption spectrum of the aerosol, based on our previous laboratory observations. The simulation results suggest that the formation of oligomers and organic acids in bulk aerosol water is unlikely to perturb aerosol surface tension significantly. Isoprene-derived organosulfates are formed in high concentrations in acidic aerosols under low-NO(x) conditions, but more experimental data are needed before the potential impact of these species on aerosol surface tension may be evaluated. Adsorption of surfactants from the gas phase may further suppress aerosol surface tension. Light absorption by aqueous aerosol SOA material is driven by dark glyoxal chemistry and is highest under high-NO(x) conditions, at high relative humidity, in the early morning hours. The wavelength dependence of the predicted absorption spectra is comparable to field observations and the predicted mass absorption efficiencies suggest that aqueous aerosol chemistry can be a significant source of aerosol brown carbon under urban conditions.

  3. Indirect estimation of absorption properties for fine aerosol particles using AATSR observations: a case study of wildfires in Russia in 2010

    NASA Astrophysics Data System (ADS)

    Rodriguez, E.; Kolmonen, P.; Virtanen, T. H.; Sogacheva, L.; Sundstrom, A.-M.; de Leeuw, G.

    2015-08-01

    The Advanced Along-Track Scanning Radiometer (AATSR) on board the ENVISAT satellite is used to study aerosol properties. The retrieval of aerosol properties from satellite data is based on the optimized fit of simulated and measured reflectances at the top of the atmosphere (TOA). The simulations are made using a radiative transfer model with a variety of representative aerosol properties. The retrieval process utilizes a combination of four aerosol components, each of which is defined by their (lognormal) size distribution and a complex refractive index: a weakly and a strongly absorbing fine-mode component, coarse mode sea salt aerosol and coarse mode desert dust aerosol). These components are externally mixed to provide the aerosol model which in turn is used to calculate the aerosol optical depth (AOD). In the AATSR aerosol retrieval algorithm, the mixing of these components is decided by minimizing the error function given by the sum of the differences between measured and calculated path radiances at 3-4 wavelengths, where the path radiances are varied by varying the aerosol component mixing ratios. The continuous variation of the fine-mode components allows for the continuous variation of the fine-mode aerosol absorption. Assuming that the correct aerosol model (i.e. the correct mixing fractions of the four components) is selected during the retrieval process, also other aerosol properties could be computed such as the single scattering albedo (SSA). Implications of this assumption regarding the ratio of the weakly/strongly absorbing fine-mode fraction are investigated in this paper by evaluating the validity of the SSA thus obtained. The SSA is indirectly estimated for aerosol plumes with moderate-to-high AOD resulting from wildfires in Russia in the summer of 2010. Together with the AOD, the SSA provides the aerosol absorbing optical depth (AAOD). The results are compared with AERONET data, i.e. AOD level 2.0 and SSA and AAOD inversion products. The RMSE

  4. Adhesion of Mineral and Soot Aerosols can Strongly Affect their Scattering and Absorption Properties

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael I.; Dlugach, Jana M.

    2012-01-01

    We use the numerically exact superposition T-matrix method to compute the optical cross sections and the Stokes scattering matrix for polydisperse mineral aerosols (modeled as homogeneous spheres) covered with a large number of much smaller soot particles. These results are compared with the Lorenz-Mie results for a uniform external mixture of mineral and soot aerosols. We show that the effect of soot particles adhering to large mineral particles can be to change the extinction and scattering cross sections and the asymmetry parameter quite substantially. The effect on the phase function and degree of linear polarization can be equally significant.

  5. Retrieval of aerosol absorption properties using the AATSR satellite instrument: a case study of wildfires over Russia 2010

    NASA Astrophysics Data System (ADS)

    Rodríguez, E.; Kolmonen, P.; Virtanen, T. H.; Sogacheva, L.; Sundström, A.-M.; de Leeuw, G.

    2014-09-01

    The retrieval of aerosol properties from satellite data is based on the optimized fit of simulated and measured radiances at the top of the atmosphere (TOA). The simulations are made using a radiative transfer model with a variety of representative aerosol properties.The optimum fit is obtained for a certain combination of aerosol components, which are externally mixed to provide the aerosol model which in turn is used to calculate the aerosol optical depth (AOD). However, other aerosol properties could be provided. In the aerosol retrieval algorithm (ADV) applied to data from the Advanced Along Track Scanning Radiometer (AATSR), four aerosol components are used, each of which is defined by their (lognormal) size distribution and a complex refractive index. The fine mode fraction is a continuous mixture of weakly and strongly absorbing components which allows for the definition of any absorbing aerosol model within the specified limits. Hence, assuming that the correct aerosol model is selected during the retrieval process, also the single scattering albedo (SSA) should correctly be retrieved. In this paper we present the SSA retrieval using the ADV algorithm by application to wildfires over Russia in the summer of 2010. Together with the AOD, the SSA provides the aerosol absorbing optical depth (AAOD). The results are compared with AERONET data, i.e. AOD level 2.0 and SSA and AAOD inversion products. The RMSE is 0.03 for SSA and 0.02 for AAOD. The SSA is further evaluated by comparison with the SSA retrieved from the Ozone Monitoring Instrument (OMI). The SSA retrieved from both instruments show similar features, but the AATSR-retrieved SSA values over areas affected by wildfires are lower.

  6. Light absorption properties of water soluble organic aerosol from Residential Wood Burning in Fresno, CA: Results from 2013 NASA DISCOVER-AQ Campaign

    NASA Astrophysics Data System (ADS)

    Kim, H.; Zhang, Q.; Young, D. E.; Parworth, C.

    2015-12-01

    Light absorption properties of water soluble organic aerosol were investigated at Fresno, CA from 13 January to 11 February, 2013 as part of the NASA DISCOVER-AQ campaign. The light absorption spectra of water soluble organic aerosol in PM2.5 was measured using a UV/vis diode array detector (DAD) coupled with a particle into liquid sampler (PILS) that sampled downstream of a PM2.5 cyclone (URG). The PILS was also coupled with two ion chromatographs (IC) to measure inorganic and organic ionic species in PM2.5. In addition, an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed at the same site to measure size-resolved chemical composition of submicrometer aerosol (PM1) in real time during this study. Light absorption at 365 nm (Abs365), which is typically used as a proxy of water-soluble brown carbon (BrC), showed strong enhancement during night time and appeared to correlate well (r = 0.71) with biomass burning organic aerosol (BBOA) from residential wood burning for heating in the Fresno area. The tight correlations between Abs365 and biomass burning relevant tracers such as acetonitrile (r = 0.69), AMS-signature ions for phenolic compounds (r = 0.52-0.71), PAH (r = 0.74), and potassium (r = 0.67) further confirm that biomass burning contributed significantly to water soluble brown carbon during this study. The absorption angstrom exponent (Åa) values fitted between 300 and 700 nm wavelength were 3.3 ± 1.1, 2.0 ± 0.9 and 4.0 ± 0.8, respectively, in the morning, afternoon and nighttime, indicating that BrC is prevalent at night in Fresno during wintertime. However, there are also indications that small amount of BrC existed during the daytime as well, likely due to daytime wood burning and other sources such as the formation of light-absorbing secondary organic aerosol (SOA). Finally, light absorption at 300 nm, 330 nm, and 390 nm were found to correlate tightly with BBOA, which indicate that biomass burning also emits

  7. Encapsulation effects on carbonaceous aerosol light absorption

    SciTech Connect

    Sedlacek, A.J.; Onasch, T.; Davidovits, P.; Cross, E.; Mazzoleni, C.

    2010-03-15

    The contribution of aerosol absorption on direct radiative forcing is still an active area of research, in part, because aerosol extinction is dominated by light scattering and, in part, because the primary absorbing aerosol of interest, soot, exhibits complex aging behavior that alters its optical properties. The consequences of this can be evidenced by the work of Ramanathan and Carmichael (2008) who suggest that incorporating the atmospheric heating due to brown clouds (plumes containing soot byproducts from automobiles, biomass burning, wood-burning kitchen stoves, and coal-fired power plants) will increase black carbon (BC) radiative forcing from the Intergovernmental Panel on Climate Change best estimate of 0.34 Wm-2 (±0.25 Wm-2) (IPCC 2007) to 0.9 Wm-2. This noteworthy degree of uncertainty is due largely to the interdependence of BC optical properties on particle mixing state and aggregate morphology, each of which changes as the particle ages in the atmosphere and becomes encapsulated within a coating of inorganic and/or organic substances. In July 2008, a laboratory-based measurement campaign, led by Boston College and Aerodyne, was initiated to begin addressing this interdependence. To achieve insights into the interdependence of BC optical properties on particle mixing state and aggregate morphology, measurements of both the optical and physical properties of flame-generated soot under nascent, coated, and denuded conditions were conducted. This poster presents data on black carbon (BC) light absorption measured by Photothermal Interferometry (Sedlacek and Lee 2007). In addition to examining nascent BC—to provide a baseline measurement—encapsulation with varying thicknesses of either dioctyl sebacate (DOS) or sulfuric acid was conducted to glean insights into the interplay between particle mixing state and optical properties. Additionally, some experiments were carried out where BC was coated and then denuded. In the case of DOS-coated soot, a

  8. Aerosol retrievals from AVHRR radiances: effects of particle nonsphericity and absorption and an updated long-term global climatology of aerosol properties

    NASA Astrophysics Data System (ADS)

    Mishchenko, M.; Geogdzhaev, I.; Liu, L.; Orgen, A.; Lacis, A.; Rossow, W.; Hovenier, J.; Volten, H.; Muñoz, O.

    2003-09-01

    The paper describes and discusses long-term global retrievals of aerosol properties from channel-1 and -2 Advanced Very High Resolution Radiometer (AVHRR) radiances. We reconfirm the previously reached conclusion that the nonsphericity of dust-like and dry sea salt aerosols can lead to very large errors in the retrieved optical thickness if one mistakenly applies the scattering model for spherical particles. Comparisons of single-scattering albedo and Ångström exponent values retrieved from the AVHRR data and those measured in situ at Sable Island indicate that the currently adopted value 0.003 can be a reasonable choice for the imaginary part of the aerosol refractive index in the global satellite retrievals. Several unexpected features in the long-term satellite record indicate a serious problem with post-launch calibration of channel-2 radiances from the NOAA-11 spacecraft. We solve this problem by using a simple re-calibration procedure removing the observed artifacts and derive a global climatology of aerosol optical thickness and size over the oceans for the period extending from July 1983 to December 1999. The global monthly mean optical thickness and Ångström exponent of tropospheric aerosols show no significant trends over the entire period and oscillate around the average values 0.145 and 0.75, respectively. The Northern hemisphere means optical thickness systematically exceeds that averaged over the Southern hemisphere. The AVHRR retrieval results during the period affected by the Mt. Pinatubo eruption are consistent with the retrievals of the stratospheric aerosol optical thickness based on Stratospheric Aerosol and Gas Experiment (SAGE) data. Time series of the aerosol optical thickness and Ângström exponent derived for four separate geographic regions exhibit varying degrees of seasonal variability controlled by local meteorological events and/or anthropogenic activities.

  9. Ultraviolet Absorption by Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Madronich, S.; Lee-Taylor, J. M.; Hodzic, A.; Aumont, B.

    2014-12-01

    Secondary organic aerosols (SOA) are typically formed in the atmosphere by the condensation of a myriad of intermediates from the photo-oxidation of volatile organic compounds (VOCs). Many of these partly oxidized molecules have functional groups (chromophores) that absorb at the ultraviolet (UV) wavelengths available in the troposphere (λ ≳ 290 nm). We used the explicit chemical model GECKO-A (Generator of Explicit Chemistry and Kinetics for Organics in the Atmosphere) to estimate UV absorption cross sections for the gaseous and particulate components of SOA from different precursors (biogenic and anthropogenic) and formed in different environments (low and high NOx, day and night). Model predictions are evaluated with laboratory and field measurements of SOA UV optical properties (esp. mass absorption coefficients and single scattering albedo), and implications are presented for surface UV radiation trends, urban actinic flux modification, and SOA lifetimes.

  10. Light absorption and morphological properties of soot-containing aerosols observed at an East Asian outflow site, Noto Peninsula, Japan

    NASA Astrophysics Data System (ADS)

    Ueda, Sayako; Nakayama, Tomoki; Taketani, Fumikazu; Adachi, Kouji; Matsuki, Atsushi; Iwamoto, Yoko; Sadanaga, Yasuhiro; Matsumi, Yutaka

    2016-03-01

    The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a thermodenuder (TD) maintained at 300 or 400 °C or a bypass line maintained at room temperature (25 °C). The average enhancement factor of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the TD at 300 °C and was found to be 1.22. The largest enhancements (> 1.30) were observed under high absorption coefficient periods when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high-density electron beam. The majority of the soot in all samples was found as mixed particles with sulfate-containing spherules or as clusters of such spherules. For samples showing high enhancement (> 1.30) of BC light absorption, the TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be thickly coated. The SP2 measurements also suggested that the proportion of thickly coated

  11. Satellite Retrieval of Aerosol Properties

    NASA Astrophysics Data System (ADS)

    de Leeuw, G.; Robles Gonzalez, C.; Kusmierczyk-Michulec, J.; Decae, R.

    SATELLITE RETRIEVAL of AEROSOL PROPERTIES G. de Leeuw, C. Robles Gonzalez, J. Kusmierczyk-Michulec and R. Decae TNO Physics and Electronics Laboratory, The Hague, The Netherlands; deleeuw@fel.tno.nl Methods to retrieve aerosol properties over land and over sea were explored. The dual view offered by the ATSR-2 aboard ERS-2 was used by Veefkind et al., 1998. The retrieved AOD (aerosol optical depth) values compare favourably with collocated sun photometer measurements, with an accuracy of 0.06 +/- 0.05 in AOD. An algorithm developed for GOME on ERS-2 takes advantage of the low surface reflection in the UV (Veefkind et al., 2000). AOD values retrieved from ATSR-2 and GOME data over western Europe are consistent. The results were used to produce a map of mean AOD values over Europe for one month (Robles-Gonzalez et al., 2000). The ATSR-2 is al- gorithm is now extended with other aerosol types with the aim to apply it over the In- dian Ocean. A new algorithm is being developed for the Ozone Monitoring Instrument (OMI) to be launched in 2003 on the NASA EOS-AURA satellite. It is expected that, based on the different scattering and absorption properties of various aerosol types, five major aerosol classes can be distinguished. The experience with the retrieval of aerosol properties by using several wavelength bands is used to develop an algorithm for Sciamachy to retrieve aerosol properties both over land and over the ocean which takes advantage of the wavelengths from the UV to the IR. The variation of the AOD with wavelength is described by the Angstrom parameter. The AOD and the Angstrom parameter together yield information on the aerosol size distribution, integrated over the column. Analysis of sunphotometer data indicates a relation between the Angstrom parameter and the mass ratio of certain aerosols (black carbon, organic carbon and sea salt) to the total particulate matter. This relation has been further explored and was applied to satellite data over land to

  12. Using the OMI Aerosol Index and Absorption Aerosol Optical Depth to evaluate the NASA MERRA Aerosol Reanalysis

    NASA Astrophysics Data System (ADS)

    Buchard, V.; da Silva, A. M.; Colarco, P. R.; Darmenov, A.; Randles, C. A.; Govindaraju, R.; Torres, O.; Campbell, J.; Spurr, R.

    2014-12-01

    A radiative transfer interface has been developed to simulate the UV Aerosol Index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI and Aerosol Absorption Optical Depth (AAOD) derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). MERRAero is based on a version of the GEOS-5 model that is radiatively coupled to the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) aerosol module and includes assimilation of Aerosol Optical Depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR), aerosol retrievals from the Aerosol Robotic Network (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain potential misplacement of plume height by the model. By sampling dust, biomass burning and pollution events in 2007 we have compared model produced AI and AAOD with the corresponding OMI products, identifying regions where the model representation of absorbing aerosols was deficient. As a result of this study over the Saharan dust region, we have obtained a new set of dust aerosol optical properties that retains consistency with the MODIS AOD data that were assimilated, while resulting in better agreement with aerosol absorption measurements from OMI. The analysis conducted over the South African and South American biomass burning regions indicates that revising the spectrally-dependent aerosol absorption properties in the near-UV region improves the modeled-observed AI comparisons

  13. Using the OMI aerosol index and absorption aerosol optical depth to evaluate the NASA MERRA Aerosol Reanalysis

    NASA Astrophysics Data System (ADS)

    Buchard, V.; da Silva, A. M.; Colarco, P. R.; Darmenov, A.; Randles, C. A.; Govindaraju, R.; Torres, O.; Campbell, J.; Spurr, R.

    2015-05-01

    A radiative transfer interface has been developed to simulate the UV aerosol index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI and aerosol absorption optical depth (AAOD) derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). MERRAero is based on a version of the GEOS-5 model that is radiatively coupled to the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) aerosol module and includes assimilation of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR), aerosol retrievals from the AErosol RObotic NETwork (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain potential misplacement of plume height by the model. By sampling dust, biomass burning and pollution events in 2007 we have compared model-produced AI and AAOD with the corresponding OMI products, identifying regions where the model representation of absorbing aerosols was deficient. As a result of this study over the Saharan dust region, we have obtained a new set of dust aerosol optical properties that retains consistency with the MODIS AOD data that were assimilated, while resulting in better agreement with aerosol absorption measurements from OMI. The analysis conducted over the southern African and South American biomass burning regions indicates that revising the spectrally dependent aerosol absorption properties in the near-UV region improves the modeled-observed AI comparisons

  14. Aerosol Angstrom Absorption Coefficient Comparisons during MILAGRO.

    NASA Astrophysics Data System (ADS)

    Marley, N. A.; Marchany-Rivera, A.; Kelley, K. L.; Mangu, A.; Gaffney, J. S.

    2007-12-01

    Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) by using a 7-channel aethalometer (Thermo- Anderson) during the month of March, 2006. The absorption measurements obtained in the field at 370, 470, 520, 590, 660, 880, and 950 nm were used to determine the aerosol Angstrom absorption exponents by linear regression. Since, unlike other absorbing aerosol species (e.g. humic like substances, nitrated PAHs), black carbon absorption is relatively constant from the ultraviolet to the infrared with an Angstrom absorption exponent of -1 (1), a comparison of the Angstrom exponents can indicate the presence of aerosol components with an enhanced UV absorption over that expected from BC content alone. The Angstrom exponents determined from the aerosol absorption measurements obtained in the field varied from - 0.7 to - 1.3 during the study and was generally lower in the afternoon than the morning hours, indicating an increase in secondary aerosol formation and photochemically generated UV absorbing species in the afternoon. Twelve-hour integrated samples of fine atmospheric aerosols (<0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. Samples were collected on quartz fiber filters with high volume impactor samplers. Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples. These continuous spectra have also been used to obtain the

  15. Scattering and absorption by thin flat aerosols.

    PubMed

    Weil, H; Chu, C M

    1980-06-15

    An integral equation method is used to study spectral and polarization effects for the scattering and absorption of electromagnetic radiation incident on arbitrarily oriented flat disk aerosols of major dimension comparable to the wavelength of the radiation. Numerical results for flat plate ice crystals are presented.

  16. Using the OMI Aerosol Index and Absorption Aerosol Optical Depth to Evaluate the NASA MERRA Aerosol Reanalysis.

    NASA Astrophysics Data System (ADS)

    Buchard, V.; da Silva, A. M., Jr.; Colarco, P. R.; Darmenov, A.; Govindaraju, R.

    2014-12-01

    A radiative transfer interface has been developed to simulate the UV Aerosol Index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). In this presentation we show comparisons of model produced AI with the corresponding OMI measurements during several months of 2007 characterized by a good sampling of dust and biomass burning events. In parallel, model produced Absorption Aerosol Optical Depth (AAOD) were compared to OMI AAOD for the same period, identifying regions where the model representation of absorbing aerosols were deficient. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, aerosol retrievals from the Aerosol Robotic Network (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain misplacement of plume height by the model.

  17. Climatology of aerosol optical properties and black carbon mass absorption cross section at a remote high-altitude site in the western Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Pandolfi, M.; Ripoll, A.; Querol, X.; Alastuey, A.

    2014-06-01

    Aerosol light scattering (σsp), backscattering (σbsp) and absorption (σap) were measured at Montsec (MSC; 42°3' N, 0°44' E, 1570 m a.s.l.), a remote high-altitude site in the western Mediterranean Basin. Mean (±SD) σsp, σbsp and σap were 18.9 ± 20.8, 2.6 ± 2.8 and 1.5 ± 1.4 Mm-1, respectively at 635 nm during the period under study (June 2011-June 2013). Mean values of single-scattering albedo (SSA, 635 nm), the scattering Ångström exponent (SAE, 450-635 nm), backscatter-to-scatter ratio (B / S, 635 nm), asymmetry parameter (g, 635 nm), black carbon mass absorption cross section (MAC, 637 nm) and PM2.5 mass scattering cross section (MSCS, 635 nm) were 0.92 ± 0.03, 1.56 ± 0.88, 0.16 ± 0.09, 0.53 ± 0.16, 10.9 ± 3.5 m2 g-1 and 2.5 ± 1.3 m2 g-1, respectively. The scattering measurements performed at MSC were in the medium/upper range of values reported by Andrews et al. (2011) for other mountaintop sites in Europe due to the frequent regional recirculation scenarios (SREG) and Saharan dust episodes (NAF) occurring mostly in spring/summer and causing the presence of polluted layers at the MSC altitude. However, the development of upslope winds and the possible presence of planetary boundary layer air at MSC altitude in summer may also have contributed to the high scattering observed. Under these summer conditions no clear diurnal cycles were observed for the measured extensive aerosol optical properties (σsp, σbsp and σap). Conversely, low σsp and σap at MSC were measured during Atlantic advections (AA) and winter regional anticyclonic episodes (WREG) typically observed during the cold season in the western Mediterranean. Therefore, a season-dependent decrease in the magnitude of aerosol extensive properties was observed when MSC was in the free troposphere, with the highest free-troposphere vs. all-data difference observed in winter and the lowest in spring/summer. The location of MSC station allowed for a reliable characterization of aerosols

  18. The Effect of Aerosol Hygroscopicity and Volatility on Aerosol Optical Properties During Southern Oxidant and Aerosol Study

    NASA Astrophysics Data System (ADS)

    Khlystov, A.; Grieshop, A. P.; Saha, P.; Subramanian, R.

    2014-12-01

    Secondary organic aerosol (SOA) from biogenic sources can influence optical properties of ambient aerosol by altering its hygroscopicity and contributing to light absorption directly via formation of brown carbon and indirectly by enhancing light absorption by black carbon ("lensing effect"). The magnitude of these effects remains highly uncertain. A set of state-of-the-art instruments was deployed at the SEARCH site near Centerville, AL during the Southern Oxidant and Aerosol Study (SOAS) campaign in summer 2013 to measure the effect of relative humidity and temperature on aerosol size distribution, composition and optical properties. Light scattering and absorption by temperature- and humidity-conditioned aerosols was measured using three photo-acoustic extinctiometers (PAX) at three wavelengths (405 nm, 532 nm, and 870 nm). The sample-conditioning system provided measurements at ambient RH, 10%RH ("dry"), 85%RH ("wet"), and 200 C ("TD"). In parallel to these measurements, a long residence time temperature-stepping thermodenuder (TD) and a variable residence time constant temperature TD in combination with three SMPS systems and an Aerosol Chemical Speciation Monitor (ACSM) were used to assess aerosol volatility and kinetics of aerosol evaporation. We will present results of the on-going analysis of the collected data set. We will show that both temperature and relative humidity have a strong effect on aerosol optical properties. SOA appears to increase aerosol light absorption by about 10%. TD measurements suggest that aerosol equilibrated fairly quickly, within 2 s. Evaporation varied substantially with ambient aerosol loading and composition and meteorology.

  19. Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass Aerosol Extinction Differential Optical Absorption Spectrometer (AE-DOAS)

    NASA Astrophysics Data System (ADS)

    Chartier, R. T.; Greenslade, M. E.

    2012-04-01

    Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

  20. Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass aerosol extinction differential optical absorption spectrometer (AE-DOAS)

    NASA Astrophysics Data System (ADS)

    Chartier, R. T.; Greenslade, M. E.

    2011-10-01

    Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

  1. Light absorption of organic aerosol from pyrolysis of corn stalk

    NASA Astrophysics Data System (ADS)

    Li, Xinghua; Chen, Yanju; Bond, Tami C.

    2016-11-01

    Organic aerosol (OA) can absorb solar radiation in the low-visible and ultra-violet wavelengths thereby modifying radiative forcing. Agricultural waste burning emits a large quantity of organic carbon in many developing countries. In this work, we improved the extraction and analysis method developed by Chen and Bond, and extended the spectral range of OC absorption. We examined light absorbing properties of primary OA from pyrolysis of corn stalk, which is a major type of agricultural wastes. Light absorption of bulk liquid extracts of OA was measured using a UV-vis recording spectrophotometer. OA can be extracted by methanol at 95%, close to full extent, and shows polar character. Light absorption of organic aerosol has strong spectral dependence (Absorption Ångström exponent = 7.7) and is not negligible at ultra-violet and low-visible regions. Higher pyrolysis temperature produced OA with higher absorption. Imaginary refractive index of organic aerosol (kOA) is 0.041 at 400 nm wavelength and 0.005 at 550 nm wavelength, respectively.

  2. Retrieval of Aerosol Absorption over Ocean using AATSR/MERIS

    NASA Astrophysics Data System (ADS)

    Filipitsch, Florian; Preusker, Rene; Fischer, Juergen

    2013-04-01

    Aerosols have a significant influence on the earth climate but are still one of the least understood variables in the earth radiation budget. On average aerosol particles scatter solar radiation back to space which leads to an offset in the global warming process to due greenhouse gases. Some types of atmospheric aerosols like black carbon or dessert dust absorb solar radiation and lead to local atmospheric warming. Even if this warming effect is overwhelmed by the cooling effect is it necessary to improve our knowledge on the global distribution of absorbing aerosols if we want to understand and predict local climate variations. Within the ESA CCI-Aerosol project we developed an innovative retrieval method to quantify aerosol absorption quantified by the Single Scattering Albedo (SSA) over the ocean in the sun glint contaminated region of a wind roughed sea surface. From satellite measurement commonly retrieved Aerosol Optical Depth (AOD), which is the vertical integrated aerosol volume extinction, gives no information on the absorbing or scattering quantities of the observed aerosol. To distinct absorption from scattering independent measurements at different viewing geometries are needed. Furthermore the reflection properties of the underlying surface has to be known and therewith distinct absorption from scattering. The dual view sensor Advanced Along-Track Scanning Radiometer (AATSR) provides such information in regions where either of the two views is sun glint effected the other is not. Hence, the sun glint is used as a lower boundary condition in the presented method an accurate determination of the ocean surface is needed. Therefore we use the 3 thermal channels from to estimate the amount of reflected sunlight to due glint in measured signal at 3.7 micrometer. The determined sun glint at the 3.7 micrometer channel is further used to derive an effective wind speed based on full radiative transfer calculations where optical properties for a wind roughed sea

  3. Aerosol Absorption Retrieval at Ultraviolet Wavelengths in a Complex Environment

    NASA Technical Reports Server (NTRS)

    Kazadzis, Stelios; Raptis, Panagiotis; Kouremeti, Natalia; Amirdis, Vassilis; Arola, Antti; Gerasopoulos, Evangelos; Schuster, Gregory L.

    2016-01-01

    We have used total and diffuse UV irradiance measurements from a multi-filter rotating shadow-band radiometer (UVMFR) in order to investigate aerosol absorption in the UV range for a 5-year period in Athens, Greece. This dataset was used as input to a radiative transfer model and the single scattering albedo (SSA) at 368 and 332 nm was calculated. Retrievals from a collocated CIMEL sun photometer were used to evaluate the products and study the absorption spectral behavior of retrieved SSA values. The UVMFR SSA, together with synchronous, CIMEL-derived retrievals of SSA at 440 nm, had a mean of 0.90, 0.87 and 0.83, with lowest values (higher absorption) encountered at the shorter wavelengths. In addition, noticeable diurnal variation of the SSA in all wavelengths is shown, with amplitudes up to 0.05. Strong SSA wavelength dependence is revealed for cases of low Angstrom exponents, accompanied by a SSA decrease with decreasing extinction optical depth, suggesting varying influence under different aerosol composition. However, part of this dependence for low aerosol optical depths is masked by the enhanced SSA retrieval uncertainty. Dust and brown carbon UV absorbing properties were also investigated to explain seasonal patterns.

  4. Aerosol absorption retrieval at ultraviolet wavelengths in a complex environment

    NASA Astrophysics Data System (ADS)

    Kazadzis, Stelios; Raptis, Panagiotis; Kouremeti, Natalia; Amiridis, Vassilis; Arola, Antti; Gerasopoulos, Evangelos; Schuster, Gregory L.

    2016-12-01

    We have used total and diffuse UV irradiance measurements from a multi-filter rotating shadow-band radiometer (UVMFR) in order to investigate aerosol absorption in the UV range for a 5-year period in Athens, Greece. This dataset was used as input to a radiative transfer model and the single scattering albedo (SSA) at 368 and 332 nm was calculated. Retrievals from a collocated CIMEL sun photometer were used to evaluate the products and study the absorption spectral behavior of retrieved SSA values. The UVMFR SSA, together with synchronous, CIMEL-derived retrievals of SSA at 440 nm, had a mean of 0.90, 0.87 and 0.83, with lowest values (higher absorption) encountered at the shorter wavelengths. In addition, noticeable diurnal variation of the SSA in all wavelengths is shown, with amplitudes up to 0.05. Strong SSA wavelength dependence is revealed for cases of low Ångström exponents, accompanied by a SSA decrease with decreasing extinction optical depth, suggesting varying influence under different aerosol composition. However, part of this dependence for low aerosol optical depths is masked by the enhanced SSA retrieval uncertainty. Dust and brown carbon UV absorbing properties were also investigated to explain seasonal patterns.

  5. Infrared Absorption by Atmospheric Aerosols in Mexico City during MILAGRO.

    NASA Astrophysics Data System (ADS)

    Kelley, K. L.; Mangu, A.; Gaffney, J. S.; Marley, N. A.

    2007-12-01

    Past research in our group using cylindrical internal reflectance spectroscopy has indicated that aqueous aerosols could contribute to the radiative warming as greenhouse species (1,2). Although aerosol radiative effects have been known for sometime and are considered one of the major uncertainties in climate change modeling, most of the studies have focused on the forcing due to scattering and absorption of radiation in the uv- visible region (3). Infrared spectral information also allows the confirmation of key functional groups that are responsible for enhanced absorption observations from secondary organics in the uv-visible region. This work extends our efforts to evaluate the infrared absorption by aerosols, particularly organics, that are now found to be a major fraction of urban and regional aerosols in the 0.1 to 1.0 micron size range and to help identify key types of organics that can contribute to aerosol absorption. During the MILAGRO campaign, quartz filter samples were taken at 12-hour intervals from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. These samples were taken at the two super-sites, T-0 (Instituto Mexicano de Petroleo in Mexico City) and T-1 (Universidad Technologica de Tecamac, State of Mexico). The samples have been characterized for total carbon content (stable isotope mass spectroscopy) and natural radionuclide tracers, as well as for their UV-visible spectroscopic properties by using integrating sphere diffuse reflectance spectroscopy (Beckman DU with a Labsphere accessory). These same samples have been characterized in the mid and near infrared spectral ranges using diffuse reflection spectroscopy (Nicolet 6700 FTIR with a Smart Collector accessory). Aerosol samples were removed from the surfaces of the aerosol filters by using Si-Carb sampler. The samples clearly indicate the presence of carbonyl organic constituents and the spectra are quite similar to those observed for humic and fulvic acids

  6. Atmospheric aerosols: Their Optical Properties and Effects

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Measured properties of atmospheric aerosol particles are presented. These include aerosol size frequency distribution and complex retractive index. The optical properties of aerosols are computed based on the presuppositions of thermodynamic equilibrium and of Mie-theory.

  7. Aerosol optical properties measurement by recently developed cavity-enhanced aerosol single scattering albedometer

    NASA Astrophysics Data System (ADS)

    Zhao, Weixiong; Xu, Xuezhe; Zhang, Qilei; Fang, Bo; Qian, Xiaodong; Chen, Weidong; Gao, Xiaoming; Zhang, Weijun

    2015-04-01

    Development of appropriate and well-adapted measurement technologies for real-time in-situ measurement of aerosol optical properties is an important step towards a more accurate and quantitative understanding of aerosol impacts on climate and the environment. Aerosol single scattering albedo (SSA, ω), the ratio between the scattering (αscat) and extinction (αext) coefficients, is an important optical parameter that governs the relative strength of the aerosol scattering and absorption capacity. Since the aerosol extinction coefficient is the sum of the absorption and scattering coefficients, a commonly used method for the determination of SSA is to separately measure two of the three optical parameters - absorption, scattering and extinction coefficients - with different instruments. However, as this method involves still different instruments for separate measurements of extinction and absorption coefficients under different sampling conditions, it might cause potential errors in the determination of SSA value, because aerosol optical properties are very sensitive to the sampling conditions such as temperature and relative humidity (RH). In this paper, we report on the development of a cavity-enhanced aerosol single scattering albedometer incorporating incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) and an integrating sphere (IS) for direct in-situ measurement of aerosol scattering and extinction coefficients on the exact same sample volume. The cavity-enhanced albedometer holds great promise for high-sensitivity and high-precision measurement of ambient aerosol scattering and extinction coefficients (hence absorption coefficient and SSA determination) and for absorbing trace gas concentration. In addition, simultaneous measurements of aerosol scattering and extinction coefficients enable a potential application for the retrieval of particle number size distribution and for faster retrieval of aerosols' complex RI. The albedometer was deployed to

  8. Measurements of Semi-volatile Aerosol and Its Effect on Aerosol Optical Properties During Southern Oxidant and Aerosol Study

    NASA Astrophysics Data System (ADS)

    Khlystov, A.; Grieshop, A. P.; Saha, P.; Subramanian, R.

    2013-12-01

    Semi-volatile compounds, including particle-bound water, comprise a large part of aerosol mass and have a significant influence on aerosol lifecycle and its optical properties. Understanding the properties of semi-volatile compounds, especially those pertaining to gas/aerosol partitioning, is of critical importance for our ability to predict concentrations and properties of ambient aerosol. A set of state-of-the-art instruments was deployed at the SEARCH site near Centerville, AL during the Southern Oxidant and Aerosol Study (SOAS) campaign in summer 2013 to measure the effect of temperature and relative humidity on aerosol size distribution, composition and optical properties. Light scattering and absorption by temperature- and humidity-conditioned aerosols was measured using three photo-acoustic extinctiometers (PAX) at three wavelengths (405 nm, 532 nm, and 870 nm). In parallel to these measurements, a long residence time temperature-stepping thermodenuder and a variable residence time constant temperature thermodenuder in combination with three SMPS systems and an Aerosol Chemical Speciation Monitor (ACSM) were used to assess aerosol volatility and kinetics of aerosol evaporation. It was found that both temperature and relative humidity have a strong effect on aerosol optical properties. The variable residence time thermodenuder data suggest that aerosol equilibrated fairly quickly, within 2 s, in contrast to other ambient observations. Preliminary analysis show that approximately 50% and 90% of total aerosol mass evaporated at temperatures of 100 C and 180C, respectively. Evaporation varied substantially with ambient aerosol loading and composition and meteorology. During course of this study, T50 (temperatures at which 50% aerosol mass evaporates) varied from 60 C to more than 120 C.

  9. Inferring Aerosol Angstrom Absorption Exponent using satellite observations

    NASA Astrophysics Data System (ADS)

    Torres, O.; Bhartia, P. K.; Jethva, H. T.; Ahn, C.

    2013-12-01

    The Angstrom Absorption Exponent (AAE) is a parameter commonly used to characterize the wavelength-dependence of aerosol absorption optical depth (AAOD). It is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellite-based method of determining the spectral AAOD of absorbing aerosols. The technique uses multi-spectral measurements of upwelling radiation from scenes where absorbing aerosols are present above clouds. The upwelling reflectance at the cloud top is attenuated by the absorption effects of the overlying aerosol layer. This attenuation effect can be described using an approximations of Beer's Law. The upwelling reflectance at the cloud-top in an aerosol-free atmospheric column is mainly a function of cloud optical depth (COD). In the proposed method of AAE derivation, the first step is determining COD which is retrieved using a previously developed color-ratio based approach. In the second step, the spectral AAOD is derived by an inversion of the measured spectral reflectance. The proposed technique will be discussed and application results making use of OMI multi-spectral measurements in the UV-Vis. will be presented.

  10. Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

    NASA Astrophysics Data System (ADS)

    Alvarado, Matthew J.; Lonsdale, Chantelle R.; Macintyre, Helen L.; Bian, Huisheng; Chin, Mian; Ridley, David A.; Heald, Colette L.; Thornhill, Kenneth L.; Anderson, Bruce E.; Cubison, Michael J.; Jimenez, Jose L.; Kondo, Yutaka; Sahu, Lokesh K.; Dibb, Jack E.; Wang, Chien

    2016-07-01

    Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10-23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction

  11. Absorption characteristics of aerosols over the northwestern region of India: Distinct seasonal signatures of biomass burning aerosols and mineral dust

    NASA Astrophysics Data System (ADS)

    Gogoi, Mukunda M.; Suresh Babu, S.; Krishna Moorthy, K.; Manoj, M. R.; Chaubey, Jai Prakash

    2013-07-01

    Continuous measurements of aerosol black carbon (BC) mass concentrations made over a period of 3 years from a semi-arid, near-coastal, remote and sparsely inhabited location along with satellite-based data of aerosol absorption index, optical depth and extinction profiles in western India are used to characterize the distinct nature of aerosols near the surface and in the free troposphere and their seasonality. Despite being far remote and sparsely inhabited, significant levels of BC are observed in the ambient during winter (1.45 ± 0.71 μg m-3) attributed to biomass burning aerosols, advected to the site from the north and west; while during summer the concentrations are far reduced (0.23 ± 0.11 μg m-3) and represent the apparent background concentrations. The spectral absorption coefficients suggest the BC during summer be mostly of fossil fuel combustions. The strong convective boundary layer dynamics produces significant diurnal variation during winter and modulates to a lesser extent the seasonal variation. Examination of aerosol (absorption) index from OMI data for the study period showed a seasonal pattern that is almost opposite to that seen at the surface; with high aerosol index in summer, showing a significant difference between the surface and columnar aerosol types in summer. MISR and MODIS-derived columnar AOD follow the OMI pattern. Analysis of the vertical profiles of aerosol extinction and volume depolarization ratio (VDR), derived from CALIPSO data indicates the presence of strong dust layers with VDR ˜ 0.3 in the altitude region 4-6 km, contributing to the high aerosol index in the OMI data, while the surface measurements show absorptive properties representing fossil fuel BC aerosols.

  12. Water absorption by secondary organic aerosol and its effect on inorganic aerosol behavior

    SciTech Connect

    Ansari, A.S.; Pandis, S.N.

    2000-01-01

    The hygroscopic nature of atmospheric aerosol has generally been associated with its inorganic fraction. In this study, a group contribution method is used to predict the water absorption of secondary organic aerosol (SOA). Compared against growth measurements of mixed inorganic-organic particles, this method appears to provide a first-order approximation in predicting SOA water absorption. The growth of common SOA species is predicted to be significantly less than common atmospheric inorganic salts such as (NH{sub 4}){sub 2}SO{sub 4} and NaCl. Using this group contribution method as a tool in predicting SOA water absorption, an integrated modeling approach is developed combining available SOA and inorganic aerosol models to predict overall aerosol behavior. The effect of SOA on water absorption and nitrate partitioning between the gas and aerosol phases is determined. On average, it appears that SOA accounts for approximately 7% of total aerosol water and increases aerosol nitrate concentrations by approximately 10%. At high relative humidity and low SOA mass fractions, the role of SOA in nitrate partitioning and its contribution to total aerosol water is negligible. However, the water absorption of SOA appears to be less sensitive to changes in relative humidity than that of inorganic species, and thus at low relative humidity and high SOA mass fraction concentrations, SOA is predicted to account for approximately 20% of total aerosol water and a 50% increase in aerosol nitrate concentrations. These findings could improve the results of modeling studies where aerosol nitrate has often been underpredicted.

  13. Volcanic Aerosol Radiative Properties

    NASA Technical Reports Server (NTRS)

    Lacis, Andrew

    2015-01-01

    Large sporadic volcanic eruptions inject large amounts of sulfur bearing gases into the stratosphere which then get photochemically converted to sulfuric acid aerosol droplets that exert a radiative cooling effect on the global climate system lasting for several years.

  14. Simulations of the Aerosol Index and the Absorption Aerosol Optical Depth and Comparisons with OMI Retrievals During ARCTAS-2008 Campaign

    NASA Technical Reports Server (NTRS)

    2010-01-01

    We have computed the Aerosol Index (AI) at 354 nm, useful for observing the presence of absorbing aerosols in the atmosphere, from aerosol simulations conducted with the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) module running online the GEOS-5 Atmospheric GCM. The model simulates five aerosol types: dust, sea salt, black carbon, organic carbon and sulfate aerosol and can be run in replay or data assimilation modes. In the assimilation mode, information's provided by the space-based MODIS and MISR sensors constrains the model aerosol state. Aerosol optical properties are then derived from the simulated mass concentration and the Al is determined at the OMI footprint using the radiative transfer code VLIDORT. In parallel, model derived Absorption Aerosol Optical Depth (AAOD) is compared with OMI retrievals. We have focused our study during ARCTAS (June - July 2008), a period with a good sampling of dust and biomass burning events. Our ultimate goal is to use OMI measurements as independent validation for our MODIS/MISR assimilation. Towards this goal we document the limitation of OMI aerosol absorption measurements on a global scale, in particular sensitivity to aerosol vertical profile and cloud contamination effects, deriving the appropriate averaging kernels. More specifically, model simulated (full) column integrated AAOD is compared with model derived Al, this way identifying those regions and conditions under which OMI cannot detect absorbing aerosols. Making use of ATrain cloud measurements from MODIS, C1oudSat and CALIPSO we also investigate the global impact on clouds on OMI derived Al, and the extent to which GEOS-5 clouds can offer a first order representation of these effects.

  15. Method and apparatus for aerosol particle absorption spectroscopy

    DOEpatents

    Campillo, Anthony J.; Lin, Horn-Bond

    1983-11-15

    A method and apparatus for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy. In another embodiment the heating beam passes through an interferometer and the scattered light reflects the Fourier Transform of the absorption spectra.

  16. Numerical simulation of infrared radiation absorption for diagnostics of gas-aerosol medium by remote sensing data

    NASA Astrophysics Data System (ADS)

    Voitsekhovskaya, O. K.; Egorov, O. V.; Kashirskii, D. E.; Shefer, O. V.

    2015-11-01

    Calculated absorption spectra of the mixture of gases (H2O, CO, CO2, NO, NO2, and SO2) and aerosol (soot and Al2O3), contained in the exhausts of aircraft and rocket engines are demonstrated. Based on the model of gas-aerosol medium, a numerical study of the spectral dependence of the absorptance for different ratios of gas and aerosol components was carried out. The influence of microphysical and optical properties of the components of the mixture on the spectral features of absorption of gas-aerosol medium was established.

  17. Aerosol absorption measurement at SWIR with water vapor interference using a differential photoacoustic spectrometer.

    PubMed

    Zhu, Wenyue; Liu, Qiang; Wu, Yi

    2015-09-07

    Atmospheric aerosol plays an important role in atmospheric radiation balance through absorbing and scattering the solar radiation, which changes local weather and global climate. Accurate measurement is highly requested to estimate the radiative effects and climate effects of atmospheric aerosol. Photoacoustic spectroscopy (PAS) technique, which observes the aerosols on their natural suspended state and is insensitive to light scattering, is commonly recognized as one of the best candidates to measure the optical absorption coefficient (OAC) of aerosols. In the present work, a method of measuring aerosol OAC at the wavelength where could also be absorbed by water vapor was proposed and corresponding measurements of the absorption properties of the atmospheric aerosol at the short wave infrared (SWIR, 1342 nm) wavelength were carried out. The spectrometer was made up of two high performance homemade photoacoustic cells. To improve the sensitivity, several methods were presented to control the noise derived from gas flow and vibration from the sampling pump. Calibration of the OAC and properties of the system were also studied in detail. Using the established PAS instrument, measurement of the optical absorption properties of the atmospheric aerosol were carried out in laboratory and field environment.

  18. In Situ Measurements of Aerosol Mass Concentration and Spectral Absorption in Xianghe, SE of Beijing, China

    NASA Astrophysics Data System (ADS)

    Chaudhry, Z.; Martins, V.; Li, Z.

    2005-12-01

    China's rapid industrialization over the last few decades has affected air quality in many regions of China, and even the regional climate. As a part of the EAST-AIRE (East Asian Study of Tropospheric Aerosols: an International Regional Experiment) study, Nuclepore filters were collected in two size ranges (PM10 and PM2.5) at 12 hour intervals since January 2005 at Xianghe, about 70 km southeast of Beijing. Each filter was analyzed for mass concentration, aerosol scattering and absorption efficiencies. Mass concentrations during the winter months (January-March) ranged from 9 to 459 μg/m3 in the coarse mode with an average concentration of 122 μg/m3, and from 11 to 203 μg/m3 in the fine mode with an average concentration of 45 μg/m3. While some of the extreme values are likely linked to local emissions, regional air pollution episodes also played important roles. Absorption efficiency measurements at 550 nm show very high values compared to measurements performed in the United States during the CLAMS experiment. The spectral mass absorption efficiency was measured from 350 to 2500 nm and shows large differences between the absorption properties of soil dust, black carbon, and organic aerosols. The strong spectral differences observed can be related to differences in refractive indices from the several collected species and particle size effects. The absorption properties from aerosols measured in China show large absorption efficiencies, compared to aerosols measured in the US, possibly linked to different technology practices used in these countries. For organic plus black carbon aerosols, where the refractive index seems to be relatively constant, the absorption efficiency spectral dependence for fine mode aerosols falls between 1/λ and 1/λ2. The coarse mode absorption shows much less spectral dependence.

  19. Sensitivity of the atmospheric temperature profile to the aerosol absorption in the presence of dust

    NASA Astrophysics Data System (ADS)

    Gómez-Amo, J. L.; di Sarra, A.; Meloni, D.

    2014-12-01

    Radiative transfer simulations in the shortwave (SW) and longwave (LW) spectral regions have been carried out to investigate the time evolution of the atmospheric heating/cooling rates and their influence on the temperature profiles under different vertical distributions of the aerosol absorption. The case study is based on measurements made at Rome, Italy, on 20 June 2007, when a dust layer was present above the urban boundary layer (BL) and the column aerosol optical depth at 550 nm was about 0.37. Column-integrated aerosol optical depth and single scattering albedo, as well as vertical profiles of aerosol extinction and meteorological variables have been derived from observations and used in the simulations. Different profiles of the aerosol absorption are considered by varying the absorption of the BL aerosols and of the desert dust, without changing the overall columnar properties. Three scenarios have been considered, with absorbing (ABL) or scattering (SBL) particles in the BL, and with a vertically homogeneous case (HL), which is taken as the reference. Calculations show that, for the selected case, about 25% of the SW heating is offset by the LW cooling within the dust layer. Different longwave/all-wave contributions are observed in the BL, depending on the BL aerosol absorption. Changes of atmospheric temperature induced by aerosol-radiation interactions only, have been investigated, while interactions with the surface through changes of the latent and sensible heat flux have been neglected. The evolution of temperature is similar for the three scenarios within the dust layer, with a daytime increase and a smaller nighttime decrease. After 24 h, the increase of the atmospheric temperature due to the aerosol radiative processes is about 1 K. In the BL, the increase of temperature is strongly dependent on the aerosol absorption capability. The oscillatory behaviour of the temperature with time in the dust layer, and the different evolution in the BL are

  20. Measurements and Modeling of Aerosol Absorption and Single Scattering Albedo at Ambient Relative Hum

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Russell, P. B.; Hamill, P.

    2000-01-01

    Uncertainties in the aerosol single scattering albedo have been identified to be an important source of errors in current large-scale model estimates of the direct aerosol radiative forcing of climate. A number of investigators have obtained estimates of the single scattering albedo from a variety of remote sensing and in situ measurements during aerosol field experiments. During the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX, 1996) for example, estimates of the aerosol single scattering albedo were obtained (1) as a best-fit parameter in comparing radiative flux changes measured by airborne pyranometer to those computed from independently measured aerosol properties; (2) from estimates of the aerosol complex index of refraction derived using a combination of airborne sunphotometer, lidar backscatter and in situ size distribution measurements; and (3) from airborne measurements of aerosol scattering and absorption using nephelometers and absorption photometers. In this paper, we briefly compare the results of the latter two methods for two TARFOX case studies, since those techniques provide height-resolved information about the aerosol single scattering albedo. Estimates of the aerosol single scattering albedo from nephelometer and absorption photometer measurements require knowledge of the scattering and absorption humidification (i.e., the increase in these properties in response to an increase in ambient relative humidity), since both measurements are usually carried out at a relative humidity different from the ambient atmosphere. In principle, the scattering humidification factor can be measured, but there is currently no technique widely available to measure the absorption of an aerosol sample as a function of relative humidity. Frequently, for lack of better knowledge, the absorption humidification is assumed to be unity (meaning that there is no change in aerosol absorption due to an increase in ambient relative humidity). This

  1. Influence of semi-volatile aerosol on physical and optical properties of aerosol in Kathmandu valley

    NASA Astrophysics Data System (ADS)

    Shrestha, Sujan; Praveen, Ps; Adhikary, Bhupesh; Shrestha, Kundan; Panday, Arnico

    2016-04-01

    A field study was conducted in the urban atmosphere of Kathmandu valley to study the influence of the semi-volatile aerosol fraction on physical and optical properties of aerosols. The study was carried out during the 2015 pre-monsoon period. Experimental setup consisted of air from an ambient air inlet being split to two sets of identical sampling instruments. The first instrument received the ambient sample directly, while the second instrument received the air sample through a thermodenuder (TDD). Four sets of experiments were conducted to understand aerosol number, size distribution, scattering and absorption properties using Condensation Particle Counter (CPC), Scanning Mobility Particle Sizer (SMPS), Aethalometer (AE33) and Nephelometer. The influence of semi-volatile aerosols was calculated from the fraction of particles evaporated in the TDD at set temparetures: room temperature, 50°C, 100°C, 150°C, 200°C, 250°C and 300°C. Results show that, with increasing temperature, the evaporated fraction of semi-volatile aerosol also increased. At room temperature the fraction of semi-volatile aerosols was 12% while at 300°C it was as high as to 49%. Aerosol size distribution analysis shows that with an increase in TDD temperature from 50°C to 300°C, peak mobility diameter of particles shifted from around 60nm to 40nm. However we found little change in effective diameter of aerosol size distribution with increase in set TDD temperature. The change in size of aerosols due to loss of semi-volatile component has a stronger influence (~70%) in higher size bins when compared to at lower size bins (~20%). Studies using the AE33 showed that absorption by black carbon (BC) is amplified due to influence of semi-volatile aerosols by upto 37% at 880nm wavelength. Similarly nephelometer measurements showed that upto 71% of total scattering was found to be contributed by semi-volatile aerosol fraction. The scattering Angstrom Exponent (SAE) of semi-volatile aerosol

  2. Using Retrieved Aerosol Spectral Properties to Characterize Aerosol Composition and Mixing

    NASA Astrophysics Data System (ADS)

    Li, J.

    2015-12-01

    The spectral dependence of aerosol properties, such as aerosol absorption optical depth (AAOD) and single scattering albedo (SSA), can be used to infer aerosol composition. In particular, aerosol mixtures dominated by dust absorption will have monotonically increasing SSA with wavelength while that dominated by black carbon absorption has monotonically decreasing SSA spectra. However, spectral AAOD and SSA measured in reality may differ from these extreme cases, due to the complicated composition and mixing states. In this study, we use spectral SSA and AAOD retrieved from AERONET measurements, assisted by CALIPSO aerosol type product and Mie calculations, to characterize aerosol mixtures over representative regions. Moreover, in addition to the monotonically increasing or decreasing AAOD and SSA spectra, we find the spectral dependence of these two parameters are frequently peaked (at 675 nm or 870 nm) over several places including East Asia, India, West Africa and South America. We thus suggest that SSA spectral curvature, defined as the negative of the second derivative of SSA as a function of wavelength, can provide additional information on the composition of these aerosol mixtures. Further analysis indicates that moderate mixing of black carbon with dust or organic carbon is mainly responsible for producing the SSA curvature. An optimization scheme was developed to match the observed AAOD and SSA spectra with Mie calculations assuming different aerosol composition and mixing states. Results suggest that while external mixing can explain most of the observed AAOD and SSA spectral dependence, internal mixing or core-shell mode is also likely under many circumstances, such as East Asia during winter and post-monsoon and winter seasons over India. This method offers the potential to quantitatively infer aerosol composition from these spectral measurements of aerosol optical properties.

  3. Aerosol particle microphotography and glare-spot absorption spectroscopy.

    PubMed

    Arnold, S; Holler, S; Li, J H; Serpengüzel, A; Auffermann, W F; Hill, S C

    1995-04-01

    The relative intensities of glare spots in the image of an electrodynamically trapped aerosol droplet are measured experimentally with an aerosol particle microscope and calculated theoretically. The theoretical calculations are in good agreement with these experiments and indicate that the intensities of these spots are extremely sensitive to the imaginary part of the refractive index. Experimentally, we obtain the molecular absorption spectrum of an impurity within a droplet by recording the spectrum of an individual glare spot produced by broadband illumination.

  4. Aerosol Forcing of Climate Change and "Anomalous" Atmospheric Absorption

    NASA Technical Reports Server (NTRS)

    Hansen, James E.

    1999-01-01

    The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well-measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. We will focus on the role of aerosols as a climate forcing mechanism and the contribution that aerosols might make to the so- called "anomalous" atmospheric absorption that has been inferred from some atmospheric measurements.

  5. Aerosol Forcing of Climate Change and Anomalous Atmospheric Absorption

    NASA Technical Reports Server (NTRS)

    Hansen, James E.

    2000-01-01

    The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change, Anthropogenic greenhouse gases (GHGs), which are well-measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. We will focus on the role of aerosols as a climate forcing mechanism and the contribution that aerosols might make to the so-called "anomalous" atmospheric absorption that has been inferred from some atmospheric measurements.

  6. CALIPSO Observations of Aerosol Properties Near Clouds

    NASA Technical Reports Server (NTRS)

    Marshak, Alexander; Varnai, Tamas; Yang, Weidong

    2010-01-01

    Clouds are surrounded by a transition zone of rapidly changing aerosol properties. Characterizing this zone is important for better understanding aerosol-cloud interactions and aerosol radiative effects as well as for improving satellite measurements of aerosol properties. We present a statistical analysis of a global dataset of CALIPSO (Cloud-Aerosol Lidar and infrared Pathfinder Satellite Observation) Lidar observations over oceans. The results show that the transition zone extends as far as 15 km away from clouds and it is ubiquitous over all oceans. The use of only high confidence level cloud-aerosol discrimination (CAD) data confirms the findings. However, the results underline the need for caution to avoid biases in studies of satellite aerosol products, aerosol-cloud interactions, and aerosol direct radiative effects.

  7. Using OMI Observations to Measure Aerosol Absorption of Biomass Burning Aerosols Above Clouds

    NASA Technical Reports Server (NTRS)

    Torres, Omar; Bhartia, P. K.; Jethva, Hiren

    2011-01-01

    The presence of absorbing aerosol layers above clouds is unambiguously detected by the TOMS/OMI UV Aerosol Index (AI) that uses satellite observations at two near-UV channels. A sensitivity study using radiative transfer calculations shows that the AI signal of resulting from the presence of aerosols above clouds is mainly driven by the aerosol absorption optical depth and the optical depth of the underlying cloud. Based on these results, an inversion algorithm has been developed to retrieve the aerosol optical depth (AOD) of aerosol layers above clouds. In this presentation we will discuss the sensitivity analysis, describe the retrieval approach, and present results of applications of the retrieval method to OMI observations over the South Atlantic Ocean. Preliminary error analyses, to be discussed, indicate that the AOD can be underestimated (up to -30%) or overestimated (up to 60%) depending on algorithmic assumptions.

  8. Equilibrium absorptive partitioning theory between multiple aerosol particle modes

    NASA Astrophysics Data System (ADS)

    Crooks, Matthew; Connolly, Paul; Topping, David; McFiggans, Gordon

    2016-10-01

    An existing equilibrium absorptive partitioning model for calculating the equilibrium gas and particle concentrations of multiple semi-volatile organics within a bulk aerosol is extended to allow for multiple involatile aerosol modes of different sizes and chemical compositions. In the bulk aerosol problem, the partitioning coefficient determines the fraction of the total concentration of semi-volatile material that is in the condensed phase of the aerosol. This work modifies this definition for multiple polydisperse aerosol modes to account for multiple condensed concentrations, one for each semi-volatile on each involatile aerosol mode. The pivotal assumption in this work is that each aerosol mode contains an involatile constituent, thus overcoming the potential problem of smaller particles evaporating completely and then condensing on the larger particles to create a monodisperse aerosol at equilibrium. A parameterisation is proposed in which the coupled non-linear system of equations is approximated by a simpler set of equations obtained by setting the organic mole fraction in the partitioning coefficient to be the same across all modes. By perturbing the condensed masses about this approximate solution a correction term is derived that accounts for many of the removed complexities. This method offers a greatly increased efficiency in calculating the solution without significant loss in accuracy, thus making it suitable for inclusion in large-scale models.

  9. Modeling the Relationships Between Aerosol Properties and the Direct and Indirect Effects of Aerosols on Climate

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.

    1994-01-01

    Aerosols may affect climate directly by scattering and absorbing visible and infrared energy, They may also affect climate indirectly by modifying the properties of clouds through microphysical processes, and by altering abundances of radiatively important gases through heterogeneous chemistry. Researchers understand which aerosol properties control the direct effect of aerosols on the radiation budget. Unfortunately, despite an abundance of data on certain types of aerosols, much work remains to be done to determine the values of these properties. For instance we have little idea about the global distribution, seasonal variation, or interannual variability of the aerosol optical depth. Also we do not know the visible light absorption properties of tropical aerosols which may contain much debris from slash and burn agriculture. A positive correlation between aerosol concentrations and albedos of marine stratus clouds is observed, and the causative microphysics is understood. However, models suggest that it is difficult to produce new particles in the marine boundary layer. Some modelers have suggested that the particles in the marine boundary layer may originate in the free troposphere and be transported into the boundary layer. Others argue that the aerosols are created in the marine boundary layer. There are no data linking aerosol concentration and cirrus cloud albedo, and models suggest cirrus properties may not be very sensitive to aerosol abundance. There is clear evidence of a radiatively significant change in the global lower stratospheric ozone abundance during the past few decades. These changes are caused by heterogeneous chemical reactions occurring on the surfaces of particles. The rates of these reactions depend upon the chemical composition of the particles. Although rapid advances in understanding heterogeneous chemistry have been made, much remains to be done.

  10. Spectral Absorption of Solar Radiation by Aerosols during ACE-Asia

    NASA Technical Reports Server (NTRS)

    Bergstrom, R. W.; Pilewskie, P.; Pommier, J.; Rabbette, M.; Russell, P. B.; Schmid, B.; Redermann, J.; Higurashi, A.; Nakajima, T.; Quinn, P. K.

    2004-01-01

    As part of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia), the upward and downward spectral solar radiant fluxes were measured with the Spectral Solar Flux Radiometer (SSFR), and the aerosol optical depth was measured with the Ames Airborne Tracking Sunphotometer (AATS-14) aboard the Center for INterdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. IN this paper, we examine the data obtained for two cases: a moderately thick aerosol layer, 12 April, and a relatively thin aerosol case, 16 April 2001. ON both days, the Twin Otter flew vertical profiles in the Korean Strait southeast of Gosan Island. For both days we determine the aerosol spectral absorption of the layer and estimate the spectral aerosol absorption optical depth and single-scattering albedo. The results for 12 April show that the single-scattering albedo increases with wavelength from 0.8 at 400 nm to 0.95 at 900 nm and remains essentially constant from 950 to 1700 nm. On 16 April the amount of aerosol absorption was very low; however, the aerosol single-scattering albedo appears to decrease slightly with wavelength in the visible region. We interpret these results in light of the two absorbing aerosol species observed during the ACE-asia study: mineral dust and black carbon. The results for 12 April are indicative of a mineral dust-black carbon mixture. The 16 April results are possibly caused by black carbon mixed with nonabsorbing pollution aerosols. For the 12 April case we attempt to estimate the relative contributions of the black carbon particles and the mineral dust particles. We compare our results with other estimates of the aerosol properties from a Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) satellite analysis and aerosol measurements made aboard the Twin Otter, aboard the National Oceanic and Atmospheric Administration Ronald H Brown ship, and at ground sites in Gosan and Japan. The results indicate a relatively complicated aerosol

  11. Application of AERONET Single Scattering Albedo and Absorption Angstrom Exponent to Classify Dominant Aerosol Types during DRAGON Campaigns

    NASA Astrophysics Data System (ADS)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Schafer, J.; Crawford, J. H.; Kim, J.; Sano, I.; Liew, S.; Salinas Cortijo, S. V.; Chew, B. N.; Lim, H.; Smirnov, A.; Sorokin, M.; Kenny, P.; Slutsker, I.

    2013-12-01

    Aerosols can have major implications on human health by inducing respiratory diseases due to inhalation of fine particles from biomass burning smoke or industrial pollution and on radiative forcing whereby the presence of absorbing aerosol particles (e.g., black carbon) increases atmospheric heating. Aerosol classification techniques have utilized aerosol loading and aerosol properties derived from multi-spectral and multi-angle observations by ground-based (e.g., AERONET) and satellite instrumentation (e.g., MISR). Aerosol Robotic Network (AERONET) data have been utilized to determine aerosol types by implementing various combinations of measured aerosol optical depth or retrieved size and absorption aerosol properties (e.g., Gobbi et al., 2007; Russell et al., 2010). Giles et al. [2012] showed single scattering albedo (SSA) relationship with extinction Angstrom exponent (EAE) can provide an estimate of the general classification of dominant aerosol types (i.e., desert dust, urban/industrial pollution, biomass burning smoke, and mixtures) based on data from ~20 AERONET sites located in known aerosol source regions. In addition, the absorption Angstrom exponent relationship with EAE can provide an indication of the dominant absorbing aerosol type such as dust, black carbon, brown carbon, or mixtures of them. These classification techniques are applied to the AERONET Level 2.0 quality assured data sets collected during Distributed Regional Aerosol Gridded Observational Network (DRAGON) campaigns in Maryland (USA), Japan, South Korea, Singapore, Penang (Malaysia), and California (USA). An analysis of aerosol type classification for DRAGON sites is performed as well as an assessment of the spatial variability of the aerosol types for selected DRAGON campaigns. Giles, D. M., B. N. Holben, T. F. Eck, A. Sinyuk, A. Smirnov, I. Slutsker, R. R. Dickerson, A. M. Thompson, and J. S. Schafer (2012), An analysis of AERONET aerosol absorption properties and classifications

  12. Chemical Properties of Combustion Aerosols: An Overview

    EPA Science Inventory

    A wide variety of pyrogenic and anthropogenic sources emit fine aerosols to the atmosphere. The physical and chemical properties of these aerosols are of interest due to their influence on climate, human health, and visibility. Aerosol chemical composition is remarkably complex. ...

  13. Biomass Burning Aerosol Absorption Measurements with MODIS Using the Critical Reflectance Method

    NASA Technical Reports Server (NTRS)

    Zhu, Li; Martins, Vanderlei J.; Remer, Lorraine A.

    2010-01-01

    This research uses the critical reflectance technique, a space-based remote sensing method, to measure the spatial distribution of aerosol absorption properties over land. Choosing two regions dominated by biomass burning aerosols, a series of sensitivity studies were undertaken to analyze the potential limitations of this method for the type of aerosol to be encountered in the selected study areas, and to show that the retrieved results are relatively insensitive to uncertainties in the assumptions used in the retrieval of smoke aerosol. The critical reflectance technique is then applied to Moderate Resolution Imaging Spectrometer (MODIS) data to retrieve the spectral aerosol single scattering albedo (SSA) in South African and South American 35 biomass burning events. The retrieved results were validated with collocated Aerosol Robotic Network (AERONET) retrievals. One standard deviation of mean MODIS retrievals match AERONET products to within 0.03, the magnitude of the AERONET uncertainty. The overlap of the two retrievals increases to 88%, allowing for measurement variance in the MODIS retrievals as well. The ensemble average of MODIS-derived SSA for the Amazon forest station is 0.92 at 670 nm, and 0.84-0.89 for the southern African savanna stations. The critical reflectance technique allows evaluation of the spatial variability of SSA, and shows that SSA in South America exhibits higher spatial variation than in South Africa. The accuracy of the retrieved aerosol SSA from MODIS data indicates that this product can help to better understand 44 how aerosols affect the regional and global climate.

  14. Measurements of the absorption coefficient of stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    Ogren, J. A.; Ahlquist, N. C.; Clarke, A. D.; Charlson, R. J.

    1981-01-01

    The absorption coefficients of stratospheric aerosols are measured using a variation on the integrating plate method. The technique is based on the decrease in the transparency of a substrate when an absorbing aerosol is deposited on it. A Lambert scatterer is placed behind the substrate to integrate forward scattered light and minimize the effect of scattering on the measurement. The low pressure in the stratosphere is used for the direct impaction of particles onto a narrow strip of opal glass. The eight samples collected had a median value of 4 x 10 to the -9th m with an uncertainty of + or - 5 x 10 to the -9th m. If this absorption is due to graphitic carbon, then its concentration is estimated at about 0.4 ng/cu m, or about 0.25% of the total aerosol mass concentration. Estimates of the aerosol scattering coefficients based on satellite extinction inversions result in an aerosol single-scattering albedo in the range of 0.96-1.0.

  15. AeroCom INSITU Project: Comparing modeled and measured aerosol optical properties

    NASA Astrophysics Data System (ADS)

    Andrews, Elisabeth; Schmeisser, Lauren; Schulz, Michael; Fiebig, Markus; Ogren, John; Bian, Huisheng; Chin, Mian; Easter, Richard; Ghan, Steve; Kokkola, Harri; Laakso, Anton; Myhre, Gunnar; Randles, Cynthia; da Silva, Arlindo; Stier, Phillip; Skeie, Ragnehild; Takemura, Toshihiko; van Noije, Twan; Zhang, Kai

    2016-04-01

    AeroCom, an open international collaboration of scientists seeking to improve global aerosol models, recently initiated a project comparing model output to in-situ, surface-based measurements of aerosol optical properties. The model/measurement comparison project, called INSITU, aims to evaluate the performance of a suite of AeroCom aerosol models with site-specific observational data in order to inform iterative improvements to model aerosol modules. Surface in-situ data has the unique property of being traceable to physical standards, which is an asset in accomplishing the overall goal of bettering the accuracy of aerosols processes and the predicative capability of global climate models. Here we compare dry, in-situ aerosol scattering and absorption data from ~75 surface, in-situ sites from various global aerosol networks (including NOAA, EUSAAR/ACTRIS and GAW) with a simulated optical properties from a suite of models participating in the AeroCom project. We report how well models reproduce aerosol climatologies for a variety of time scales, aerosol characteristics and behaviors (e.g., aerosol persistence and the systematic relationships between aerosol optical properties), and aerosol trends. Though INSITU is a multi-year endeavor, preliminary phases of the analysis suggest substantial model biases in absorption and scattering coefficients compared to surface measurements, though the sign and magnitude of the bias varies with location. Spatial patterns in the biases highlight model weaknesses, e.g., the inability of models to properly simulate aerosol characteristics at sites with complex topography. Additionally, differences in modeled and measured systematic variability of aerosol optical properties suggest that some models are not accurately capturing specific aerosol behaviors, for example, the tendency of in-situ single scattering albedo to decrease with decreasing aerosol extinction coefficient. The endgoal of the INSITU project is to identify specific

  16. Critical Reflectance Derived from MODIS: Application for the Retrieval of Aerosol Absorption over Desert Regions

    NASA Technical Reports Server (NTRS)

    Wells, Kelley C.; Martins, J. Vanderlei; Remer, Lorraine A.; Kreidenweis, Sonia M.; Stephens, Graeme L.

    2012-01-01

    Aerosols are tiny suspended particles in the atmosphere that scatter and absorb sunlight. Smoke particles are aerosols, as are sea salt, particulate pollution and airborne dust. When you look down at the earth from space sometimes you can see vast palls of whitish smoke or brownish dust being transported by winds. The reason that you can see these aerosols is because they are reflecting incoming sunlight back to the view in space. The reason for the difference in color between the different types of aerosol is that the particles arc also absorbing sunlight at different wavelengths. Dust appears brownish or reddish because it absorbs light in the blue wavelengths and scatters more reddish light to space, Knowing how much light is scattered versus how much is absorbed, and knowin that as a function of wavelength is essential to being able to quantify the role aerosols play in the energy balance of the earth and in climate change. It is not easy measuring the absorption properties of aerosols when they are suspended in the atmosphere. People have been doing this one substance at a time in the laboratory, but substances mix when they are in the atmosphere and the net absorption effect of all the particles in a column of air is a goal of remote sensing that has not yet been completely successful. In this paper we use a technique based on observing the point at which aerosols change from brightening the surface beneath to darkening it. If aerosols brighten a surface. they must scatter more light to space. If they darken the surface. they must be absorbing more. That cross over point is called the critical reflectance and in this paper we show that critical reflectance is a monotonic function of the intrinsic absorption properties of the particles. This parameter we call the single scattering albedo. We apply the technique to MODIS imagery over the Sahara and Sahel regions to retrieve the single scattering albedo in seven wavelengths, compare these retrievals to ground

  17. Cloud Scavenging Effects on Aerosol Radiative and Cloud-nucleating Properties - Final Technical Report

    SciTech Connect

    Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

    2009-03-05

    The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

  18. Cloud-Driven Changes in Aerosol Optical Properties - Final Technical Report

    SciTech Connect

    Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

    2007-09-30

    The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

  19. Synergic use of TOMS and Aeronet Observations for Characterization of Aerosol Absorption

    NASA Technical Reports Server (NTRS)

    Torres, O.; Bhartia, P. K.; Dubovik, O.; Holben, B.; Siniuk, A.

    2003-01-01

    The role of aerosol absorption on the radiative transfer balance of the earth-atmosphere system is one of the largest sources of uncertainty in the analysis of global climate change. Global measurements of aerosol single scattering albedo are, therefore, necessary to properly assess the radiative forcing effect of aerosols. Remote sensing of aerosol absorption is currently carried out using both ground (Aerosol Robotic Network) and space (Total Ozone Mapping Spectrometer) based observations. The satellite technique uses measurements of backscattered near ultraviolet radiation. Carbonaceous aerosols, resulting from the combustion of biomass, are one of the most predominant absorbing aerosol types in the atmosphere. In this presentation, TOMS and AERONET retrievals of single scattering albedo of carbonaceous aerosols, are compared for different environmental conditions: agriculture related biomass burning in South America and Africa and peat fires in Eastern Europe. The AERONET and TOMS derived aerosol absorption information are in good quantitative agreement. The most absorbing smoke is detected over the African Savanna. Aerosol absorption over the Brazilian rain forest is less absorbing. Absorption by aerosol particles resulting from peat fires in Eastern Europe is weaker than the absorption measured in Africa and South America. This analysis shows that the near UV satellite method of aerosol absorption characterization has the sensitivity to distinguish different levels of aerosol absorption. The analysis of the combined AERONET-TOMS observations shows a high degree of synergy between satellite and ground based observations.

  20. Variability of Aerosol Optical Properties at Four North American Surface Monitoring Sites.

    NASA Astrophysics Data System (ADS)

    Delene, David J.; Ogren, John A.

    2002-03-01

    Aerosol optical properties measured over several years at surface monitoring stations located at Bondville, Illinois (BND); Lamont, Oklahoma (SGP); Sable Island, Nova Scotia (WSA); and Barrow, Alaska (BRW), have been analyzed to determine the importance of the variability in aerosol optical properties to direct aerosol radiative forcing calculations. The amount of aerosol present is of primary importance and the aerosol optical properties are of secondary importance to direct aerosol radiative forcing calculations. The mean aerosol light absorption coefficient (ap) is 10 times larger and the mean aerosol scattering coefficient (sp) is 5 times larger at the anthropogenically influenced site at BND than at BRW. The aerosol optical properties of single scattering albedo (o) and hemispheric backscatter fraction (b) have variability of approximately ±3% and ±8%, respectively, in mean values among the four stations. To assess the importance of the variability in o and b on top of the atmosphere aerosol radiative forcing calculations, the aerosol radiative forcing efficiency (F/) is calculated. The F/ is defined as the aerosol forcing (F) per unit optical depth () and does not depend explicitly on the amount of aerosol present. Based on measurements at four North American stations, radiative transfer calculations that assume fixed aerosol properties can have errors of 1%-6% in the annual average forcing at the top of the atmosphere due to variations in average single scattering albedo and backscatter fraction among the sites studied. The errors increase when shorter-term variations in aerosol properties are considered; for monthly and hourly timescales, errors are expected to be greater than 8% and 15%, respectively, approximately one-third of the time. Systematic relationships exist between various aerosol optical properties [ap, o, b, F/, and Ångström exponent (å)] and the amount of aerosol present (measured by sp) that are qualitatively similar but quantitatively

  1. Variability of aerosol optical properties in the Western Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Pandolfi, M.; Cusack, M.; Alastuey, A.; Querol, X.

    2011-08-01

    Aerosol light scattering, absorption and particulate matter (PM) concentrations were measured at Montseny, a regional background site in the Western Mediterranean Basin (WMB) which is part of the European Supersite for Atmospheric Aerosol Research (EUSAAR). Off line analyses of 24 h PM filters collected with Hi-Vol instruments were performed for the determination of the main chemical components of PM. Mean scattering and hemispheric backscattering coefficients (@ 635 nm) were 26.6±23.2 Mm-1 and 4.3±2.7 Mm-1, respectively and the mean aerosol absorption coefficient (@ 637 nm) was 2.8±2.2 Mm-1. Mean values of Single Scattering Albedo (SSA) and Ångström exponent (å) (calculated from 450 nm to 635 nm) at MSY were 0.90±0.05 and 1.3±0.5 respectively. A clear relationship was observed between the PM1/PM10 and PM2.5/PM10 ratios as a function of the calculated Ångström exponents. Mass scattering cross sections (MSC) for fine mass and sulfate at 635 nm were 2.8±0.5 m2 g-1 and 11.8±2.2 m2 g-1, respectively, while the mean aerosol absorption cross section (MAC) was 10.4±2.0 m2 g-1. The variability in aerosol optical properties in the WMB were largely explained by the origin and ageing of air masses over the measurement site. The MAC values appear dependent of particles aging: similar to the expected absorption cross-section for fresh emissions under Atlantic Advection episodes and higher under aerosol pollution episodes. The analysis of the Ångström exponent as a function of the origin the air masses revealed that polluted winter anticyclonic conditions and summer recirculation scenarios typical of the WMB led to an increase of fine particles in the atmosphere (å = 1.5±0.1) while the aerosol optical properties under Atlantic Advection episodes and Saharan dust outbreaks were clearly dominated by coarser particles (å = 1.0±0.4). The sea breeze played an important role in transporting pollutants from the developed WMB coastlines towards inland rural areas

  2. Is There a Common Correction for Biases in Historic Filter-Based Aerosol Absorption Measurements?

    NASA Astrophysics Data System (ADS)

    McComiskey, A. C.; Jefferson, A.; Dubey, M. K.; Aiken, A. C.; Fast, J. D.; Flynn, C. J.; Kassianov, E.

    2014-12-01

    Improved characterization of aerosol absorption is a pressing need for improving estimates of climate forcing by aerosols. Measurements of aerosol absorption are difficult to make with the accuracy and precision demanded by climate science. While several different approaches have been employed and new techniques have emerged, none can yet be considered a true 'gold standard'. Instruments that use filter-based methods have been the most widely used and are the basis of historic records. However, several studies using direct photoacoustic techniques have shown that filter-based measurements can be biased relative to these direct measurements. It has been demonstrated that this bias depends strongly on aerosol chemical composition, specifically concentration of organic mass. The wealth of information in the extensive set of historical filter-based data demands that this bias be diagnosed and corrected. A correction is critical for proper evaluation and development of chemical transport models, improved retrievals from remote sensing measurements, and integrating aerosol absorption surface and sub-orbital in situ measurements with knowledge gained from these other approaches. We have performed an intercomparison of absorption coefficients from a photoacoustic and two filter-based instruments with co-located organic mass concentrations from continuous, half-hourly averaged measurements over six months at a remote, continental site in the US (ARM SGP). The results show a bias in the filter-based measurements with organic concentration that is consistent with previous studies. Previous results come from controlled lab studies or field campaigns where absorption coefficients and organic concentrations are high and may represent aerosol close to the source. The current study is important in that these quantities are much lower and the aerosol likely more aged, representing a larger portion of the global conditions, yet shows a similar bias. This site provides other measures

  3. Retrieval of Aerosol Profiles using Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS)

    NASA Astrophysics Data System (ADS)

    Yilmaz, Selami; Frieß, Udo; Apituley, Arnoud; Henzing, Bas; Baars, Holger; Heese, Birgit; Althausen, Dietrich; Adam, Mariana; Putaud, Jean-Philippe; Zieger, Paul; Platt, Ulrich

    2010-05-01

    Multi Axis Differential Absorption Spectroscopy (MAX-DOAS) is a well established measurement technique to derive atmospheric trace gas profiles. Using MAX-DOAS measurements of trace gases with a known vertical profile, like the oxygen-dimer O4, it is possible to retrieve information on atmospheric aerosols. Based on the optimal estimation method, we have developed an algorithm which fits simultaneously measured O4 optical densities and relative intensities at several wavelengths and elevation angles to values simulated by a radiative transfer model. Retrieval parameters are aerosol extinction profile and optical properties such as single scattering albedo, phase function and Angström exponent. In 2008 and 2009 several intercomparison campaigns with established aerosol measurement techniques took place in Cabauw/Netherlands, Melpitz/Germany, Ispra/Italy and Leipzig/Germany, where simultaneous DOAS, lidar, Sun photometer and Nephelometer measurements were performed. Here we present results of the intercomparisons for cloud free conditions. The correlation of the aerosol optical thickness retrieved by the DOAS technique and the Sun photometer shows coefficients of determination from 0.96 to 0.98 and slopes from 0.94 to 1.07. The vertical structure of the DOAS retrieved aerosol extinction profiles compare favourably with the structures seen by the backscatter lidar. However, the vertical spatial development of the boundary layer is reproduced with a lower resolution by the DOAS technique. Strategies for the near real-time retrieval of trace gas profiles, aerosol profiles and optical properties will be discussed as well.

  4. Asian Aerosols: A Geophysical Fluid Dynamics Laboratory general circulation model sensitivity study of model response to aerosol optical depth and aerosol absorption

    NASA Astrophysics Data System (ADS)

    Randles, C. A.; Ramaswamy, V.

    2007-12-01

    Atmospheric absorption by black carbon (BC) aerosol heats the atmosphere while simultaneously cooling the surface and reducing latent and sensible heat fluxes from the land. Recent studies have shown that absorbing BC aerosol can have a large impact on regional climates, including modification of the hydrological cycle. However, significant uncertainties remain with regards to (a) the total amount of all aerosol species and (b) the amount of aerosol absorption. Here we present a GCM sensitivity study focusing on the influences due to total aerosol amount and aerosol absorption in the south and east Asian regions. Six experiments are conducted to test the equilibrium response of the GFDL AM2 GCM (under conditions of prescribed, observed sea surface temperatures) to (i) changes in aerosol absorption caused by changes in BC aerosol amount, and (ii) aerosol extinction optical depth increases corresponding to the year 1990 relative to a control case of 1950. In order to systematically explore the uncertainties in aerosol loading and absorption, the sensitivity experiments are classified into four regimes: low extinction optical depth, low absorption; low extinction optical depth, high absorption; high extinction optical depth, low absorption; and high extinction optical depth, high absorption. Changes in surface temperature and changes in the hydrological cycle are generally insignificant when lower aerosol extinction optical depths are considered. For higher extinction optical depths, the change in the modeled regional circulation relative to the control circulation over south and east Asia is affected by the amount of aerosol absorption and contrasts sharply to the regional circulation change associated with increasing only scattering aerosols. When increasing absorbing aerosols over the region, low-level convergence and increases in vertical velocity overcome the stabilizing effects of the absorbing aerosol and enhance the monsoonal circulation and precipitation rate

  5. Black carbon and wavelength-dependent aerosol absorption in the North China Plain based on two-year aethalometer measurements

    NASA Astrophysics Data System (ADS)

    Ran, L.; Deng, Z. Z.; Wang, P. C.; Xia, X. A.

    2016-10-01

    Light-absorbing components of atmospheric aerosols have gained particular attention in recent years due to their climatic and environmental effects. Based on two-year measurements of aerosol absorption at seven wavelengths, aerosol absorption properties and black carbon (BC) were investigated in the North China Plain (NCP), one of the most densely populated and polluted regions in the world. Aerosol absorption was stronger in fall and the heating season (from November to March) than in spring and summer at all seven wavelengths. Similar spectral dependence of aerosol absorption was observed in non-heating seasons despite substantially strong absorption in fall. With an average absorption Angström exponent (α) of 1.36 in non-heating seasons, freshly emitted BC from local fossil fuel burning was thought to be the major component of light-absorbing aerosols. In the heating season, strong ultraviolet absorption led to an average α of 1.81, clearly indicating the importance of non-BC light-absorbing components, which were possibly from coal burning for domestic heating and aging processes on a regional scale. Diurnally, the variation of BC mass concentrations experienced a double-peak pattern with a higher level at night throughout the year. However, the diurnal cycle of α in the heating season was distinctly different from that in non-heating seasons. α peaked in the late afternoon in non-heating seasons with concomitantly observed low valley in BC mass concentrations. In contrast, α peaked around the midnight in the heating season and lowered down during the daytime. The relationship of aerosol absorption and winds in non-heating seasons also differed from that in the heating season. BC mass concentrations declined while α increased with increasing wind speed in non-heating seasons, which suggested elevated non-BC light absorbers in transported aged aerosols. No apparent dependence of α on wind speed was found in the heating season, probably due to well mixed

  6. Retrieval of Aerosol Profiles using Multi Axis Differential Absorption Spectroscopy (MAX-DOAS)

    NASA Astrophysics Data System (ADS)

    Yilmaz, S.; Friess, U.; Apituley, A.; de Leeuw, G.; Platt, U.

    2009-04-01

    Multi Axis Differential Absorption Spectroscopy (MAX-DOAS) is a well established measurement technique to derive atmospheric trace gas profiles. Using MAX-DOAS measurements of trace gases with a known vertical profile, like the oxygen-dimer O4, it is possible to retrieve information on atmospheric aerosols. Based on the optimal estimation method, we have developed an algorithm which fits simultaneously measured O4 optical densities at several wavelengths and elevation angles to values simulated by a radiative transfer model. Retrieval parameters are aerosol extinction profile and optical properties like single scattering albedo, phase function and Angström exponent. In the scope of a joint research activity of the EU funded project EUSAAR (European Supersites for Atmospheric Aerosol Research) we have developed a new kind of DOAS instrument, which uses three miniature spectrometers to cover the near-ultraviolet to visible wavelength range (290-790nm), enabling to capture all absorption bands of the oxygen-dimer O4. Additionally, it is possible to point to any direction in the sky with a 2D telescope unit which is connected to the spectrometers via fiber optics. In May 2008, an intercomparison campaign with established aerosol measurement techniques took place in Cabauw/Netherlands, where simultaneous DOAS, LIDAR, Sun photometer and Nephelometer measurements were performed. We present first results of selected days from this period. The optical properties of aerosols retrieved by the DOAS measurement technique show very promising qualitative agreement with the established measurement techniques demonstrating the progress towards our goal of establishing the MAX-DOAS technique for retrieving optical properties of atmospheric aerosols. Quantitative comparison is ongoing.

  7. Mixing state and spectral absorption of atmospheric aerosols observed at a marine background site

    NASA Astrophysics Data System (ADS)

    Cayetano, M. G.; Lee, K. Y.; Kim, Y. J.

    2011-12-01

    Mineral dust and sea salt particles are portions of atmospheric aerosols in Korea due to the periodic transport of loess dust particles from Gobi and Taklimakan deserts in west China, as well as the sea salt enrichment of atmospheric particles from the seas surrounding the Korean peninsula [Kim et al., 2009; Sahu et al., 2009]. Carbonaceous particles and secondary inorganic aerosols (sulphates and nitrates) are ubiquitous due to the proliferating biomass burning [Ryu et al., 2004], as well as the increasing use of fossil fuels locally and by regional transport from neighbouring countries. Collectively, when these aerosols are transported, their compositions are further modified due to the aging process, impacting their physico-chemical properties including spectral absorption. In order to investigate the spectral response of the absorption under different ambient aerosol conditions, measurements have been conducted at a marine background site in Korea (Deokjeok Island. 37° 13' 33" N, 126° 8' 51" E) during the spring (13 days) and fall (8 days) seasons of 2009 using an aethalometer (Magee AE31), a nephelometer (Optec NGN2a) and other supporting instruments (PILS-IC, PM2.5 cyclone samplers for off-line OC/EC measurements). It has been found that spring aerosols were dominated by sulphate-rich and carbonaceous-rich fractions (21.4%±8.0% and 28.8%±7.9%, respectively), with an Angström exponent of absorption, αabs = 1.3±0.1 at 370-950 nm. The fall season aerosols were grouped based on their chemical composition as acidic aerosols, dust-enriched, and seasalt-enriched aerosols. Angström exponent of absorption, αabs for acidic aerosols was obtained to be 1.3±0.2 at 370-950 nm. However, dust enriched aerosols showed increased absorption in the short UV-Vis range (370-590 nm), which can be attributed to their mixing with light absorbing aerosols. Different types of aerosols exhibit different spectral absorption characteristics depending on their composition and

  8. Mass absorption indices of various types of natural aerosol particles in the infrared.

    PubMed

    Fischer, K

    1975-12-01

    The mass absorption index of aerosol particles has been measured in the 2-17-microm wavelength region. The measurements were performed on films of aerosol particles that were collected by an automatic jet impactor at polluted and various uncontaminated remote sites. All but marine aerosols possess strong absorption bands in the transparent part of the atmospheric long-wave spectrum, indicating marked influence of aerosol particles on the radiation budget of the atmosphere.

  9. Refractive Index and Absorption Attribution of Highly Absorbing Brown Carbon Aerosols from an Urban Indian City-Kanpur

    NASA Astrophysics Data System (ADS)

    Shamjad, P. M.; Tripathi, S. N.; Thamban, Navaneeth M.; Vreeland, Heidi

    2016-11-01

    Atmospheric aerosols influence Earth’s radiative balance, having both warming and cooling effects. Though many aerosols reflect radiation, carbonaceous aerosols such as black carbon and certain organic carbon species known as brown carbon have the potential to warm the atmosphere by absorbing light. Black carbon absorbs light over the entire solar spectrum whereas brown carbon absorbs near-UV wavelengths and, to a lesser extent, visible light. In developing countries, such as India, where combustion sources are prolific, the influence of brown carbon on absorption may be significant. In order to better characterize brown carbon, we present experimental and modeled absorption properties of submicron aerosols measured in an urban Indian city (Kanpur). Brown carbon here is found to be fivefold more absorbing at 365 nm wavelength compared to previous studies. Results suggest ~30% of total absorption in Kanpur is attributed to brown carbon, with primary organic aerosols contributing more than secondary organics. We report the spectral brown carbon refractive indices along with an experimentally constrained estimate of the influence of aerosol mixing state on absorption. We conclude that brown carbon in Kanpur is highly absorbing in nature and that the mixing state plays an important role in light absorption from volatile species.

  10. Refractive Index and Absorption Attribution of Highly Absorbing Brown Carbon Aerosols from an Urban Indian City-Kanpur.

    PubMed

    Shamjad, P M; Tripathi, S N; Thamban, Navaneeth M; Vreeland, Heidi

    2016-11-24

    Atmospheric aerosols influence Earth's radiative balance, having both warming and cooling effects. Though many aerosols reflect radiation, carbonaceous aerosols such as black carbon and certain organic carbon species known as brown carbon have the potential to warm the atmosphere by absorbing light. Black carbon absorbs light over the entire solar spectrum whereas brown carbon absorbs near-UV wavelengths and, to a lesser extent, visible light. In developing countries, such as India, where combustion sources are prolific, the influence of brown carbon on absorption may be significant. In order to better characterize brown carbon, we present experimental and modeled absorption properties of submicron aerosols measured in an urban Indian city (Kanpur). Brown carbon here is found to be fivefold more absorbing at 365 nm wavelength compared to previous studies. Results suggest ~30% of total absorption in Kanpur is attributed to brown carbon, with primary organic aerosols contributing more than secondary organics. We report the spectral brown carbon refractive indices along with an experimentally constrained estimate of the influence of aerosol mixing state on absorption. We conclude that brown carbon in Kanpur is highly absorbing in nature and that the mixing state plays an important role in light absorption from volatile species.

  11. Refractive Index and Absorption Attribution of Highly Absorbing Brown Carbon Aerosols from an Urban Indian City-Kanpur

    PubMed Central

    Shamjad, P. M.; Tripathi, S. N.; Thamban, Navaneeth M.; Vreeland, Heidi

    2016-01-01

    Atmospheric aerosols influence Earth’s radiative balance, having both warming and cooling effects. Though many aerosols reflect radiation, carbonaceous aerosols such as black carbon and certain organic carbon species known as brown carbon have the potential to warm the atmosphere by absorbing light. Black carbon absorbs light over the entire solar spectrum whereas brown carbon absorbs near-UV wavelengths and, to a lesser extent, visible light. In developing countries, such as India, where combustion sources are prolific, the influence of brown carbon on absorption may be significant. In order to better characterize brown carbon, we present experimental and modeled absorption properties of submicron aerosols measured in an urban Indian city (Kanpur). Brown carbon here is found to be fivefold more absorbing at 365 nm wavelength compared to previous studies. Results suggest ~30% of total absorption in Kanpur is attributed to brown carbon, with primary organic aerosols contributing more than secondary organics. We report the spectral brown carbon refractive indices along with an experimentally constrained estimate of the influence of aerosol mixing state on absorption. We conclude that brown carbon in Kanpur is highly absorbing in nature and that the mixing state plays an important role in light absorption from volatile species. PMID:27883083

  12. Aerosol Absorption Retrievals from the PACE Broad Spectrum Ocean Color Instrument (OCI)

    NASA Technical Reports Server (NTRS)

    Mattoo, Shana; Remer, Lorraine A.; Levy, Robert C.; Gupta, Pawan; Ahmad, Ziauddin; Martins, J. Vanderlei; Lima, Adriana Rocha; Torres, Omar

    2016-01-01

    The PACE (Pre-­Aerosol, Clouds and ocean Ecosystem) mission, anticipated for launch in the early 2020s, is designed to characterize oceanic and atmospheric properties. The primary instrument on-­-board will be a moderate resolution (approximately 1 km nadir) radiometer, called the Ocean Color Instrument (OCI). OCI will provide high spectral resolution (5 nm) from the UV to NIR (350 - 800 nm), with additional spectral bands in the NIR and SWIR. The OCI itself is an excellent instrument for atmospheric objectives, providing measurements across a broad spectral range that in essence combines the capabilities of MODIS and OMI, but with the UV channels from OMI to be available at moderate resolution. (Image credit: PACE Science Definition Team Report). Objective: Can we make use of the UV-­SWIR measurements to derive information about aerosol absorption when aerosol loading is high?

  13. Properties of aerosol processed by ice clouds

    NASA Astrophysics Data System (ADS)

    Rudich, Y.; Adler, G.; Moise, T.; Erlick-Haspel, C.

    2012-12-01

    We suggest that highly porous aerosol (HPA) can form in the upper troposphere/lower stratosphere when ice particles encounter sub-saturation leading to ice sublimation similar to freeze drying. This process can occur at the lower layers of cirrus clouds (few km), at anvils of high convective clouds and thunderstorms, in clouds forming in atmospheric gravitational waves, in contrails and in high convective clouds injecting to the stratosphere. A new experimental system that simulates freeze drying of proxies for atmospheric aerosol at atmospheric pressure was constructed and various proxies for atmospheric soluble aerosol were studied. The properties of resulting HPA were characterized by various methods. It was found that the resulting aerosol have larger sizes (extent depends on substance and mixing), lower density (largevoid fraction), lower optical extinction and higher CCN activity and IN activity. Implication of HPA's unique properties and their atmospheric consequences to aerosol processing in ice clouds and to cloud cycles will be discussed.

  14. Global Analysis of Aerosol Properties Above Clouds

    NASA Technical Reports Server (NTRS)

    Waquet, F.; Peers, F.; Ducos, F.; Goloub, P.; Platnick, S. E.; Riedi, J.; Tanre, D.; Thieuleux, F.

    2013-01-01

    The seasonal and spatial varability of Aerosol Above Cloud (AAC) properties are derived from passive satellite data for the year 2008. A significant amount of aerosols are transported above liquid water clouds on the global scale. For particles in the fine mode (i.e., radius smaller than 0.3 m), including both clear sky and AAC retrievals increases the global mean aerosol optical thickness by 25(+/- 6%). The two main regions with man-made AAC are the tropical Southeast Atlantic, for biomass burning aerosols, and the North Pacific, mainly for pollutants. Man-made AAC are also detected over the Arctic during the spring. Mineral dust particles are detected above clouds within the so-called dust belt region (5-40 N). AAC may cause a warming effect and bias the retrieval of the cloud properties. This study will then help to better quantify the impacts of aerosols on clouds and climate.

  15. Absorbing aerosols over Asia: A Geophysical Fluid Dynamics Laboratory general circulation model sensitivity study of model response to aerosol optical depth and aerosol absorption

    NASA Astrophysics Data System (ADS)

    Randles, C. A.; Ramaswamy, V.

    2008-11-01

    Forcing by absorbing atmospheric black carbon (BC) tends to heat the atmosphere, cool the surface, and reduce the surface latent and sensible heat fluxes. BC aerosol can have a large impact on regional climates and the hydrologic cycle. However, significant uncertainties remain concerning the increases in (1) the total amount of all aerosol species and (2) the amount of aerosol absorption that may have occurred over the 1950-1990 period. Focusing on south and east Asia, the sensitivity of a general circulation model's climate response (with prescribed sea surface temperatures and aerosol distributions) to such changes is investigated by considering a range of both aerosol absorption and aerosol extinction optical depth increases. We include direct and semidirect aerosol effects only. Precipitation changes are less sensitive to changes in aerosol absorption optical depth at lower aerosol loadings. At higher-extinction optical depths, low-level convergence and increases in vertical velocity overcome the stabilizing effects of absorbing aerosols and enhance the monsoonal circulation and precipitation in northwestern India. In contrast, the presence of increases in only scattering aerosols weakens the monsoonal circulation and inhibits precipitation here. Cloud amount changes can enhance or counteract surface solar flux reduction depending on the aerosol loading and absorption, with the changes also influencing the surface temperature and the surface energy balance. The results have implications for aerosol reduction strategies in the future that seek to mitigate air pollution concerns. At higher optical depths, if absorbing aerosol is present, reduction of scattering aerosol alone has a reduced effect on precipitation changes, implying that reductions in BC aerosols should be undertaken at the same time as reductions in sulfate aerosols.

  16. Aerosol physical properties from satellite horizon inversion

    NASA Technical Reports Server (NTRS)

    Gray, C. R.; Malchow, H. L.; Merritt, D. C.; Var, R. E.; Whitney, C. K.

    1973-01-01

    The feasibility is investigated of determining the physical properties of aerosols globally in the altitude region of 10 to 100 km from a satellite horizon scanning experiment. The investigation utilizes a horizon inversion technique previously developed and extended. Aerosol physical properties such as number density, size distribution, and the real and imaginary components of the index of refraction are demonstrated to be invertible in the aerosol size ranges (0.01-0.1 microns), (0.1-1.0 microns), (1.0-10 microns). Extensions of previously developed radiative transfer models and recursive inversion algorithms are displayed.

  17. Global Aerosol Radiative Forcing Derived from Sea WiFS-Inferred Aerosol Optical Properties

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah; Chan, Pui-King; Wang, Menghua

    1999-01-01

    Aerosol optical properties inferred from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) radiance measurements are used to compute the aerosol shortwave radiative forcing using a radiative transfer model. The aerosol optical thickness at the wavelength of 865-nm is taken from the SeaWIFS archive. It is found that the nominal optical thickness over oceans ranges from 0.1 to 0.2. Using a maritime aerosol model and the radiances measured at the various SeaWiFS channels, the Angstrom exponent is determined to be 0.2174, the single-scattering albedo to be 0.995, and the asymmetry factor to be 0.786. The radiative transfer model has eight bands in the visible and ultraviolet spectral regions and three bands in the near infrared. It includes the absorption due to aerosols, water vapor, carbon dioxide, and oxygen, and the scattering due to aerosols and gases (Rayleigh scattering). The radiative forcing is computed over global oceans for four months (January, April, July, and October, 1998) to represent four seasons. It is found that the aerosol radiative forcing is large and changes significantly with seasons near the continents with large-scale forest fires and desert dust. Averaged over oceans and the four months, the aerosol radiative forcing is approximately 7 W/sq m at the top of the atmosphere. This large radiative forcing is expected to have a significant cooling effect on the Earth's climate as implied from simulations of a number of general circulation models.

  18. Aerosol Optical Properties Measured Onboard the Ronald H. Brown During ACE Asia as a Function of Aerosol Chemical Composition and Source Region

    NASA Technical Reports Server (NTRS)

    Quinn, P. K.; Coffman, D. J.; Bates, T. S.; Welton, E. J.; Covert, D. S.; Miller, T. L.; Johnson, J. E.; Maria, S.; Russell, L.; Arimoto, R.

    2004-01-01

    During the ACE Asia intensive field campaign conducted in the spring of 2001 aerosol properties were measured onboard the R/V Ronald H. Brown to study the effects of the Asian aerosol on atmospheric chemistry and climate in downwind regions. Aerosol properties measured in the marine boundary layer included chemical composition; number size distribution; and light scattering, hemispheric backscattering, and absorption coefficients. In addition, optical depth and vertical profiles of aerosol 180 deg backscatter were measured. Aerosol within the ACE Asia study region was found to be a complex mixture resulting from marine, pollution, volcanic, and dust sources. Presented here as a function of air mass source region are the mass fractions of the dominant aerosol chemical components, the fraction of the scattering measured at the surface due to each component, mass scattering efficiencies of the individual components, aerosol scattering and absorption coefficients, single scattering albedo, Angstrom exponents, optical depth, and vertical profiles of aerosol extinction. All results except aerosol optical depth and the vertical profiles of aerosol extinction are reported at a relative humidity of 55 +/- 5%. An over-determined data set was collected so that measured and calculated aerosol properties could be compared, internal consistency in the data set could be assessed, and sources of uncertainty could be identified. By taking into account non-sphericity of the dust aerosol, calculated and measured aerosol mass and scattering coefficients agreed within overall experimental uncertainties. Differences between measured and calculated aerosol absorption coefficients were not within reasonable uncertainty limits, however, and may indicate the inability of Mie theory and the assumption of internally mixed homogeneous spheres to predict absorption by the ACE Asia aerosol. Mass scattering efficiencies of non-sea salt sulfate aerosol, sea salt, submicron particulate organic

  19. Atmospheric aerosols: Their Optical Properties and Effects (supplement)

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A digest of technical papers is presented. Topics include aerosol size distribution from spectral attenuation with scattering measurements; comparison of extinction and backscattering coefficients for measured and analytic stratospheric aerosol size distributions; using hybrid methods to solve problems in radiative transfer and in multiple scattering; blue moon phenomena; absorption refractive index of aerosols in the Denver pollution cloud; a two dimensional stratospheric model of the dispersion of aerosols from the Fuego volcanic eruption; the variation of the aerosol volume to light scattering coefficient; spectrophone in situ measurements of the absorption of visible light by aerosols; a reassessment of the Krakatoa volcanic turbidity, and multiple scattering in the sky radiance.

  20. Remote Sensing of Aerosol Properties during CARES

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Pekour, Mikhail S.; Flynn, Connor J.; Ferrare, R.; Hostetler, Chris A.; Hair, John; Jobson, Bertram Thomas

    2011-10-01

    One month of MFRSR data collected at two sites in the central California (USA) region during the CARES campaign are processed and the MFRSR-derived AODs at 500 nm wavelength are compared with available AODs provided by AERONET measurements. We find that the MFRSR and AERONET AODs are small ({approx}0.05) and comparable. A reasonable quantitative agreement between column aerosol size distributions (up to 2 um) from the MFRSR and AERONET retrievals is illustrated as well. Analysis of the retrieved (MFRSR and AERONET) and in situ measured aerosol size distributions suggests that the contribution of the coarse mode to aerosol optical properties is substantial for several days. The results of a radiative closure experiment performed for the two sites and one-month period show a favorable agreement between the calculated and measured broadband downwelling irradiances (bias does not exceed about 3 Wm-2), and thus imply that the MFRSR-derived aerosol optical properties are reasonable.

  1. Aerosol absorption measurement with a sinusoidal phase modulating fiber optic photo thermal interferometer

    NASA Astrophysics Data System (ADS)

    Li, Shuwang; Shao, Shiyong; Mei, Haiping; Rao, Ruizhong

    2016-10-01

    Aerosol light absorption plays an important role in the earth's atmosphere direct and semi-direct radiate forcing, simultaneously, it also has a huge influence on the visibility impairment and laser engineering application. Although various methods have been developed for measuring aerosol light absorption, huge challenge still remains in precision, accuracy and temporal resolution. The main reason is that, as a part of aerosol light extinction, aerosol light absorption always generates synchronously with aerosol light scattering, and unfortunately aerosol light scattering is much stronger in most cases. Here, a novel photo-thermal interferometry is proposed only for aerosol absorption measurement without disturbance from aerosol scattering. The photo-thermal interferometry consists of a sinusoidal phase-modulating single mode fiber-optic interferometer. The thermal dissipation, caused by aerosol energy from photo-thermal conversion when irritated by pump laser through interferometer, is detected. This approach is completely insensitive to aerosol scattering, and the single mode fiber-optic interferometer is compact, low-cost and insensitive to the polarization shading. The theory of this technique is illustrated, followed by the basic structure of the sinusoidal phase-modulating fiber-optic interferometer and demodulation algorithms. Qualitative and quantitative analysis results show that the new photo-thermal interference is a potential approach for aerosol absorption detection and environmental pollution detection.

  2. Spectral Measurements of Aerosol Absorption from UV to VISIBLE

    NASA Astrophysics Data System (ADS)

    Krotkov, N. A.; Labow, G.; Herman, J.; Bhartia, P. K.; Slusser, J.; Durham, B.; Janson, G.; Wilson, C.; Disterhoft, P.; Cede, A.; Abuhassan, N.; Eck, T. F.; Holben, B.; Bais, A.; Rapsomanikis, S.

    2007-05-01

    Amount of solar radiation reaching the Earth's surface can be strongly influenced by aerosol absorption. The aerosol absorption optical thickness (AAOT) in the visible and near IR (440 nm- 1020nm) is routinely produced from almucantar measurements made by the CIMEL instruments in the AERONET network. AAOT in the UV (300nm- 368nm) have been derived from the total and diffuse hemispherical flux measurements made by UV- Multifilter Rotating Shadowband Radiometer (UV-MFRSR, Yankee Environmental Systems, Inc.) instruments. However, no direct comparisons between these two methods exist because the CIMEL wavelengths (used in almucantar retrievals) do not overlap with the UV-MFRSR wavelengths. To enable direct comparisons between the two techniques, we have modified our UV-MFRSR, part of USDA UVB Monitoring and Research Network, by replacing standard 300nm filter with 440nm filter used in AERONET network. The instrument has been deployed at Mauna Loa Observatory, at NASA GSFC in Greenbelt, MD (July 2005 - June 2006) and during SCOUT-03 field campaign in Thessaloniki, Greece in July 2006. During these deployments the instrument's calibration was monitored daily using co-located AERONET and BREWER direct sun measurements of aerosol extinction optical thickness (AOT). Between the deployments the instrument was thoroughly calibrated at the NOAA Central UV Calibration Facility in Boulder, Colorado. We find that the UV-MSFRSR instrument is highly susceptible to calibration drifts. However, these drifts can be accurately assessed using AERONET and BREWER direct sun data. After correcting for these calibration changes, the AAOT was inferred by fitting the measurements of global and diffuse atmospheric transmittances with the forward RT model independently at each spectral channel. The AOT data and ancillary measurements of aerosol column particle size distribution and refractive index in the visible wavelengths (by CIMEL sun-sky almucantar inversions), direct -sun column NO2 and

  3. Infrared absorption by volcanic stratospheric aerosols observed by ISAMS

    SciTech Connect

    Grainger, R.G.; Lambert, A.; Taylor, F.W.; Remedios, J.J.; Rodgers, C.D.; Corney, M. ); Kerridge, B.J. )

    1993-06-18

    The upper atmosphere research satellite was lofted shortly after the Mt. Pinatubo volcano erupted, and is estimated to have injected 20 million metric tons of sulphur dioxide into the stratosphere. This gas typically is converted to sulphuric acid by interactions with water droplets in the stratosphere. These droplets are typically not saturated in acid density, so the sticking fraction is very high. The improved stratospheric and mesospheric sounder makes measurements in 14 infrared channels from 4 to 17 [mu]m. The authors have used the available infrared data channels to model the distribution and density of sulfuric acid aerosols in the stratospheric band about the equator as a result of this volcanic eruption. Knowing the spectral properties of the aerosol load will aid in modeling the radiative and climatic impacts of this volcanic ejecta.

  4. Light absorption properties of brown carbon in the high Himalayas

    NASA Astrophysics Data System (ADS)

    Kirillova, Elena N.; Marinoni, Angela; Bonasoni, Paolo; Vuillermoz, Elisa; Facchini, Maria Cristina; Fuzzi, Sandro; Decesari, Stefano

    2016-08-01

    The light-absorbing properties of water-soluble brown carbon (WS-BrC) and methanol-soluble brown carbon (MeS-BrC) were studied in PM10 aerosols collected at the "Nepal Climate Observatory-Pyramid" (NCO-P) station (5079 m above sea level) during the period 2013-2014. The light absorption coefficients of WS-BrC and MeS-BrC were the highest during the premonsoon season and the lowest during monsoon. MeS-BrC absorbs about 2 times higher at 365 nm and about 3 times more at 550 nm compared to WS-BrC. The mass absorption cross section (MAC) of WS-BrC measured at 365 nm is similar to that observed previously at South Asian low-altitude sites. Fractional solar radiation absorption by BrC compared to BC considering the full solar spectrum showed that WS-BrC absorbs 4 ± 1% and MeS-BrC absorbs 9 ± 2% compared to BC at NCO-P. Such ratios become 8 ± 1% (for WS-BrC respect to BC) and 17 ± 5% (for MeS-BrC respect to BC) when accounting for correction factors proposed by previous studies to convert absorption coefficients in bulk solutions into light absorption by accumulation mode aerosol particles. These results confirm the importance of BrC in contributing to light-absorbing aerosols in this region of the world. However, the BrC absorption at 550 nm appears small compared to that of BC (1-5%, or 3-9% with conversion factors), and it is lower compared to global model estimates constrained by Aerosol Robotic Network observations. Finally, our study provides no clear evidence of a change in the fractional contribution of BrC with respect to BC to light absorption in the middle troposphere respect to the Indo-Gangetic plain boundary layer.

  5. Light absorption by secondary organic aerosol from α-pinene: Effects of oxidants, seed aerosol acidity, and relative humidity

    SciTech Connect

    Song, Chen; Gyawali, Madhu; Zaveri, Rahul A.; Shilling, John E.; Arnott, W. Patrick

    2013-10-25

    It is well known that light absorption from dust and black carbon aerosols has a warming effect on climate while light scattering from sulfate, nitrate, and sea salt aerosols has a cooling effect. However, there are large uncertainties associated with light absorption and scattering by different types of organic aerosols, especially in the near-UV and UV spectral regions. In this paper, we present the results from a systematic laboratory study focused on measuring light absorption by secondary organic aerosols (SOAs) generated from dark α-pinene + O3 and α-pinene + NOx + O3 systems in the presence of neutral and acidic sulfate seed aerosols. Light absorption was monitored using photoacoustic spectrometers at four different wavelengths: 355, 405, 532, and 870 nm. Significant light absorption at 355 and 405 nm was observed for the SOA formed from α-pinene + O3 + NO3 system only in the presence of highly acidic sulfate seed aerosols under dry conditions. In contrast, no absorption was observed when the relative humidity was elevated to greater than 27% or in the presence of neutral sulfate seed aerosols. Organic nitrates in the SOA formed in the presence of neutral sulfate seed aerosols were found to be nonabsorbing, while the light-absorbing compounds are speculated to be aldol condensation oligomers with nitroxy organosulfate groups that are formed in highly acidic sulfate aerosols. Finally and overall, these results suggest that dark α-pinene + O3 and α-pinene + NOx + O3 systems do not form light-absorbing SOA under typical atmospheric conditions.

  6. Light Absorption in the Stratosphere: Trend, Soot Aerosol Concentration and Contribution by...

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Verma, S.; Strwwa, A. W.; Ferry, G. V.; Hamill, P.; Vay, S.; Gore, Warren J. Y. (Technical Monitor)

    1997-01-01

    The light absorption coefficient, Beta(a) of the stratospheric aerosol is an important quantity that determines its radiative effects. When combined with the aerosol scattering coefficient, Beta(a) it becomes possible to evaluate the aerosol single scatter albedo, omega = Beta(s)/(Beta(s) + Beta(a)) which is essential for modeling the overall radiative effects of the stratospheric aerosol. Pollack1 determined that omega = 0.98 is a critical value that separates stratospheric cooling from warming.

  7. Relationship between carbonaceous components and aerosol light absorption during winter at an urban site of Gwangju, Korea

    NASA Astrophysics Data System (ADS)

    Park, Seung Shik; Son, Se-Chang

    2017-03-01

    To examine the relationship between the chemical composition of light-absorbing organic aerosols and the absorption properties of the aerosols, daily PM2.5 samples were collected during winter at an urban site of Gwangju, Korea, and analyzed for organic carbon and elemental carbon (OC and EC), water-soluble organic carbon (WSOC), humic-like substances (HULIS), and water-soluble inorganic substances. The real-time black carbon (BC) concentration in PM2.5 was also measured using a dual-spot aethalometer. During the study period, average WSOC/OC and HULIS-C/WSOC ratios were 0.53 and 0.52, respectively. K+/EC and K+/OC ratios indicate that biomass burning (BB) emissions are a possible source of the observed carbonaceous aerosols and K+. Moderate-to-strong correlations of HULIS with NO3-, oxalate, SO42 -, K+, CO, and ΔBC (= BC@370 nm - BC@880 nm) suggest that in addition to the primary BB emissions, secondary processing is another important contributor to the formation of HULIS in winter at the site. The average absorption Ångstrӧm exponent (α) of fine aerosols for the wavelengths of 370-950 nm and 590-950 nm was 1.29 and 1.18, respectively, but the aerosol α value was higher in the near UV wavelength range (370-520 nm), with an average of 1.51 (0.76-2.36), indicating that aerosol absorption characteristics during winter were influenced by BB aerosol sources, as well as by traffic emissions. Over the study period, the α370-520 nm value during the highest EC, highest OC, and Asian dust events was 1.42 ± 0.10 (1.26-1.59), 1.44 ± 0.15 (1.16-1.68), and 1.90 ± 0.28 (1.54-2.36), respectively. Higher α370-520 nm values during the Asian dust event were attributed to the influence of dust particles. In addition, the light absorption coefficients of aerosols at 370 nm were strongly correlated with OC (R2 = 0.76), water-insoluble OC (R2 = 0.70), and water-soluble HULIS (R2 = 0.64). These tight correlations suggest that water-insoluble fractions of OC, as well as the

  8. Analysis of aerosol optical and microphysical properties observed during the DC3 field study

    NASA Astrophysics Data System (ADS)

    Chen, G.; Schuster, G. L.; Anderson, B. E.; Jimenez, J. L.; Campuzano Jost, P.; Dibb, J. E.; Scheuer, E. M.; Ziemba, L. D.; Beyersdorf, A. J.; Thornhill, K. L.; Moore, R.; Winstead, E.; Markovic, M. Z.

    2013-12-01

    The Deep Convective Clouds and Chemistry Experiment (DC3) consisted of 18 research flights from Salina, KS. During cloud inflow and outflow surveys, various aged aerosol layers and plumes, including biomass burning, were sampled by the NASA DC-8 aircraft which was equipped with a broad suite of instruments for aerosol optical, microphysical, and chemical properties. As a result, the DC3 dataset includes detailed aerosol number size distribution, bulk aerosol mass concentration, black carbon mass concentration, and mass size distribution for sulfate, nitrate, ammonium and organics, together with scattering and absorption coefficients. We use this comprehensive dataset to perform a detailed closure analysis to examine the consistency between the observed aerosol properties and the literature reported aerosol refractive index values. In this context, we report aerosol observations, and comparisons between the aerosol mass and number size distribution for various aerosol layers. Closure tests will also be presented in terms of the impact of the aerosol composition and size distribution on the scattering and absorption.

  9. Atmospheric Aerosol Properties and Climate Impacts

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Kahn, Ralph A.; Remer, Lorraine A.; Yu, Hongbin; Rind, David; Feingold, Graham; Quinn, Patricia K.; Schwartz, Stephen E.; Streets, David G.; DeCola, Phillip; Halthore, Rangasayi

    2009-01-01

    This report critically reviews current knowledge about global distributions and properties of atmospheric aerosols, as they relate to aerosol impacts on climate. It assesses possible next steps aimed at substantially reducing uncertainties in aerosol radiative forcing estimates. Current measurement techniques and modeling approaches are summarized, providing context. As a part of the Synthesis and Assessment Product in the Climate Change Science Program, this assessment builds upon recent related assessments, including the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4, 2007) and other Climate Change Science Program reports. The objectives of this report are (1) to promote a consensus about the knowledge base for climate change decision support, and (2) to provide a synthesis and integration of the current knowledge of the climate-relevant impacts of anthropogenic aerosols for policy makers, policy analysts, and general public, both within and outside the U.S government and worldwide.

  10. A Comparison of Aerosol Optical Property Measurements Made During the DOE Aerosol Intensive Operating Period and Their Effects on Regional Climate

    NASA Technical Reports Server (NTRS)

    Strawa, Anthony W.; Hallar, A. G.; Arnott, W. P.; Covert, D.; Elleman, R.; Ogren, J.; Schmid, B.; Luu, A.

    2004-01-01

    The amount of radiant energy an aerosol absorbs has profound effects on climate and air quality. It is ironic that aerosol absorption coefficient is one of the most difficult to measure aerosol properties. One of the main purposes of the DOE Aerosol Intensive Operating Period (IOP) flown in May, 2003 was to assess our ability to measure absorption coefficient in situ. This paper compares measurements of aerosol optical properties made during the IOP. Measurements of aerosol absorption coefficient were made by Particle Soot Absorption Photometer (PSAP) aboard the CIRPAS Twin-Otter (U. Washington) and on the DOE Cessna 172 (NOAA-C,MDL). Aerosol absorption coefficient was also measured by a photoacoustic instrument (DRI) that was operated on an aircraft for the first time during the IOP. A new cavity ring-down (CRD) instrument, called Cadenza (NASA-AkC), measures the aerosol extinction coefficient for 675 nm and 1550 nm light, and simultaneously measures the scattering coefficient at 675 nm. Absorption coefficient is obtained from the difference of measured extinction and scattering within the instrument. Measurements of absorption coefficient from all of these instruments during appropriate periods are compared. During the IOP, several significant aerosol layers were sampled aloft. These layers are identified in the remote (AATS-14) as well as in situ measurements. Extinction profiles measured by Cadenza are compared to those derived from the Ames Airborne Tracking Sunphotometer (AATS-14, NASA-ARC). The regional radiative impact of these layers is assessed by using the measured aerosol optical properties in a radiative transfer model.

  11. Aerosol Light Absorption and Scattering Assessments and the Impact of City Size on Air Pollution

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, Guadalupe

    The general problem of urban pollution and its relation to the city population is examined in this dissertation. A simple model suggests that pollutant concentrations should scale approximately with the square root of city population. This model and its experimental evaluation presented here serve as important guidelines for urban planning and attainment of air quality standards including the limits that air pollution places on city population. The model was evaluated using measurements of air pollution. Optical properties of aerosol pollutants such as light absorption and scattering plus chemical species mass concentrations were measured with a photoacoustic spectrometer, a reciprocal nephelometer, and an aerosol mass spectrometer in Mexico City in the context of the multinational project "Megacity Initiative: Local And Global Research Observations (MILAGRO)" in March 2006. Aerosol light absorption and scattering measurements were also obtained for Reno and Las Vegas, NV USA in December 2008-March 2009 and January-February 2003, respectively. In all three cities, the morning scattering peak occurs a few hours later than the absorption peak due to the formation of secondary photochemically produced aerosols. In particular, for Mexico City we determined the fraction of photochemically generated secondary aerosols to be about 75% of total aerosol mass concentration at its peak near midday. The simple 2-d box model suggests that commonly emitted primary air pollutant (e.g., black carbon) mass concentrations scale approximately as the square root of the urban population. This argument extends to the absorption coefficient, as it is approximately proportional to the black carbon mass concentration. Since urban secondary pollutants form through photochemical reactions involving primary precursors, in linear approximation their mass concentration also should scale with the square root of population. Therefore, the scattering coefficient, a proxy for particulate matter

  12. Study of aerosol radiative properties under different relative humidity conditions in the thermal infrared region

    NASA Astrophysics Data System (ADS)

    Kuo, C. P.; Yang, P.; Nasiri, S. L.; Liu, X.

    2014-12-01

    In the aerosol transport process, the optical properties of aerosol particles can vary due to humidification or mixing with other kinds of aerosols. Previous studies have shown mixing dust with other types of aerosol tends to make the aerosol more spectrally absorptive, but the degree of impact of relative humidity (RH) along the transport path is not clear. To investigate this effect, we conduct a numerical study to estimate the radiative sensitivity of aerosols under various relative humidity conditions. Specifically, the OPAC (Optical Properties of Aerosols and Clouds) database is used, which provides the optical properties (i.e., the extinction, scattering and absorption coefficient, single-scattering albedo, asymmetry factor and phase function) of ten types of aerosols under various relative humidity conditions. Lookup tables (LUTs) of the bidirectional reflectivity, transmissivity and effective emissivity will be computed for the ten aerosol types for input to the high-spectral-resolution radiative transfer model (HRTM). Using these LUTs, the HTRM can calculate top-of-atmospheric brightness temperatures, which we can use to determine the degree of radiative sensitivity in the infrared spectral region. Furthermore, comparisons between simulations and MODIS observations will be presented.

  13. Vertically Resolved Aerosol Optical Properties over the ARM SGP Site

    NASA Technical Reports Server (NTRS)

    Schmid, B.; Jonsson, H.; Strawa, A.; Provencal, B.; Covert, D.; Arnott, P.; Bucholtz, A.; Pilewskie, P.; Pommier, J.; Rissman, T.

    2003-01-01

    In order to meet one of its goals - to relate observations of radiative fluxes and radiances to the atmospheric composition - the Department of Energy's Atmospheric Radiation Measurement (ARM) program has pursued measurements and modeling activities that attempt to determine how aerosols impact atmospheric radiative transfer, both directly and indirectly. However, significant discrepancies between aerosol properties measured in situ or remotely remain. To this end, the ARM program will conduct an Aerosol Intensive Operational Period (IOP) in May 2003 at the ARM Southern Great Plains (SGP) site in north central Oklahoma. The IOP involves airborne measurements from two airplanes over the heavily instrumented SGP site. We will give an overview of early airborne results obtained aboard Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. The aircraft will carry instrumentation to perform in-situ measurements of aerosol absorption, scattering, extinction and particle size including such novel techniques as the photoacoustic and cavity ring-down methods. Aerosol optical depth and extinction will be measured with the NASA Ames Airborne Tracking 14-channel sunphotometer. Furthermore up- and downwelling solar (broadband and spectral) and infrared radiation will be measured using three different instruments. The up-looking radiation instruments will be mounted on a newly developed stabilized platform, which will keep the instruments level up to aircraft pitch and roll angles of 10 degrees. Additional effort will be directed toward measurement of cloud condensation nucleus concentration as a function of supersaturation and relating CCN concentration to aerosol composition and size distribution. This relation is central to description of the aerosol indirect effect.

  14. Morphology and Optical Properties of Mixed Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Fard, Mehrnoush M.; Krieger, Ulrich; Rudich, Yinon; Marcolli, Claudia; Peter, Thomas

    2015-04-01

    Experiments and modeling studies have shown that deliquesced aerosols can be present not only as one-phase system containing organics, inorganic salts and water, but often as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase 1,2. Recent laboratory studies conducted with model mixtures representing tropospheric aerosols1,2,3, secondary organic aerosol (SOA) from smog chamber experiments4, and field measurements5 suggest that liquid- liquid phase separations (LLPS) is indeed a common phenomenon in mixed organic/ ammonium sulfate (AS) particles. During LLPS, particles may adopt different morphologies mainly core- shell and partially engulfed. A core- shell configuration will have consequences for heterogeneous chemistry and hygroscopicity and as a result will alter the optical properties of the particles since the aqueous inorganic-rich phase will be totally enclosed by a probably highly viscous organic coating with low diffusivity for reactants and water. The primary objective of this project is to establish a method for investigating the morphology of mixed inorganic and absorbing organic compounds of atmospheric relevance and study their radiative properties before, during, and after phase transitions mainly during LLPS. This will be the first study looking into the radiative effect of LLPS in detail. In this first experiment, the behavior of single droplets of carminic acid (CA)/ AS/ H2O mixture was monitored during relative humidity (RH) cycles using optical microscopy. The same mixture particle was levitated in an electrodynamic balance (EDB) and the change in its absorption properties was measured at varying RH. We also intend to determine the occurrence of LLPS in accumulation- sized particles and the change in their absorption using a cavity ring down aerosol spectrometer. If LLPS alters the absorptive properties of the suggested model aerosols significantly, absorption measurements of accumulation mode

  15. Impact of Tropospheric Aerosol Absorption on Ozone Retrieval from buv Measurements

    NASA Technical Reports Server (NTRS)

    Torres, O.; Bhartia, P. K.

    1998-01-01

    The impact of tropospheric aerosols on the retrieval of column ozone amounts using spaceborne measurements of backscattered ultraviolet radiation is examined. Using radiative transfer calculations, we show that uv-absorbing desert dust may introduce errors as large as 10% in ozone column amount, depending on the aerosol layer height and optical depth. Smaller errors are produced by carbonaceous aerosols that result from biomass burning. Though the error is produced by complex interactions between ozone absorption (both stratospheric and tropospheric), aerosol scattering, and aerosol absorption, a surprisingly simple correction procedure reduces the error to about 1%, for a variety of aerosols and for a wide range of aerosol loading. Comparison of the corrected TOMS data with operational data indicates that though the zonal mean total ozone derived from TOMS are not significantly affected by these errors, localized affects in the tropics can be large enough to seriously affect the studies of tropospheric ozone that are currently undergoing using the TOMS data.

  16. Strong Wavelength Dependence of Aerosol Light Absorption from Peat Combustion

    NASA Astrophysics Data System (ADS)

    Gyawali, M. S.; Chakrabarty, R. K.; Yatavelli, R. L. N.; Chen, L. W. A. A.; Knue, J.; Samburova, V.; Watts, A.; Moosmüller, H.; Arnott, W. P.; Wang, X.; Zielinska, B.; Chow, J. C.; Watson, J. G.; Tsibart, A.

    2014-12-01

    Globally, organic soils and peats may store as much as 600 Gt of terrestrial carbon, representing 20 - 30% of the planet's terrestrial organic carbon mass. This is approximately the same carbon mass as that contained in Earth's atmosphere, despite peatlands occupying only 3% of its surface. Effects of fires in these ecosystems are of global concern due to their potential for enormous carbon release into the atmosphere. The implications for contributions of peat fires to the global carbon cycle and radiative forcing scenarios are significant. Combustion of peat mostly takes place in the low temperature, smoldering phase of a fire. It consumes carbon that may have accumulated over a period of hundreds to thousands of years. In comparison, combustion of aboveground biomass fuels releases carbon that has accumulated much more recently, generally over a period of years or decades. Here, we report our findings on characterization of emissions from laboratory combustion of peat soils from three locations representing the biomes in which these soils occur. Peat samples from Alaska and Florida (USA) and Siberia (Russia) were burned at two different fuel moisture levels. Burns were conducted in an 8-m3 volume combustion chamber located at the Desert Research Institute, Reno, NV, USA. We report significant brown carbon production from combustion of all three peat soils. We used a multispectral (405, 532, 781 nm) photoacoustic instrument equipped with integrating nephelometer to measure the wavelength-dependent aerosol light absorption and scattering. Absorption Ångström exponents (between 405 and 532 nm) as high as ten were observed, revealing strongly enhanced aerosol light absorption in the violet and blue wavelengths. Single scattering albedos (SSA) of 0.94 and 0.99 were observed at 405 and 532 nm, respectively, for the same sample. Variability of these optical parameters will be discussed as a function of fuel and combustion conditions. Other real-time measurements

  17. Atmospheric Optical Properties and Spectral Analysis of Desert Aerosols

    NASA Astrophysics Data System (ADS)

    Yvgeni, D.; Karnieli, A.; Kaufman, Y. J.; Andreae, M. O.; Holben, B. N.; Maenhaut, W.

    2002-05-01

    Scientific background Aerosols can interact directly with solar and terrestrial radiation by scattering as well as absorption. In addition, they can indirectly alter the planetary albedo by modifying the properties of clouds. Objectives Investigations have been devoted to two main areas: (1) Aerosol climatology situation in the Negev desert, investigations of physical and chemical characteristics of aerosols, and study of the local and long-range transport trajectory of polluted air masses over the Negev desert; and (2) An estimation of the optical properties throughout the atmospheric column by surface measurements via performance of spectral and statistical analysis of the data received from two measurement systems. Results and conclusions Analyzed data from the Sede Boker site, in the Negev Desert of Israel, shows an increase in aerosol optical depth during the summer seasons and a decrease during winter. One of the possible reasons for this characteristic is an increase of the precipitable water (reaches 3.0-3.5 cm) due to a constant wind stream from the Mediterranean Sea in same time. The highest probability distribution of the aerosol optical depth is in the range of 0.15-0.20; and of the Angstrom parameter is in range of 0.83 - 1.07. During dust storm events, the scattering coefficient range at 670 nm and 440 nm wavelengths were inverted. It was discovered that the dust particles in this case had non-spherical character. Comparison between optical depth, measured through all atmospheric column, and scattering coefficient from surface measurements provides correlation coefficient (r) equal to 0.64. The Angstrom parameter, calculated via optical depth and via scattering coefficient, provides a correlation coefficient of 0.66. Thus we can obtain an estimate of the influence of the surface aerosol situation on column optical properties. The combined analysis of dust cloud altitude and optical depth as a function of the time indicates long-term transport and

  18. Physical and Chemical Properties of Anthropogenic Aerosols: An overview

    EPA Science Inventory

    A wide variety of anthropogenic sources emit fine aerosols to the atmosphere. The physical and chemical properties of these aerosols are of interest due to their influence on climate, human health, and visibility. Aerosol chemical composition is complex. Combustion aerosols can c...

  19. Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol.

    PubMed

    Martinsson, J; Eriksson, A C; Nielsen, I Elbæk; Malmborg, V Berg; Ahlberg, E; Andersen, C; Lindgren, R; Nyström, R; Nordin, E Z; Brune, W H; Svenningsson, B; Swietlicki, E; Boman, C; Pagels, J H

    2015-12-15

    The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Ångström exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.

  20. Investigation the optical and radiative properties of aerosol vertical profile of boundary layer by lidar and ground based measurements

    NASA Astrophysics Data System (ADS)

    Chen, W.; Chou, C.; Lin, P.; Wang, S.

    2011-12-01

    The planetary boundary layer is the air layer near the ground directly affected by diurnal heat, moisture, aerosol, and cloud transfer to or from the surface. In the daytime solar radiation heats the surface, initiating thermal instability or convection. Whereas, the scattering and absorption of aerosols or clouds might decrease the surface radiation or heat atmosphere which induce feedbacks such as the enhanced stratification and change in relative humidity in the boundary layer. This study is aimed to understand the possible radiative effect of aerosols basing on ground based aerosol measurements and lidar installed in National Taiwan University in Taipei. The optical and radiative properties of aerosols are dominated by aerosol composition, particle size, hygroscopicity property, and shape. In this study, aerosol instruments including integrating nephelometer, open air nephelometer, aethalometer are applied to investigate the relationship between aerosol hygroscopicity properties and aerosol types. The aerosol hygroscopicity properties are further applied to investigate the effect of relative humidity on aerosol vertical profiles measured by a dual-wavelength and depolarization lidar. The possible radiative effect of aerosols are approached by vertical atmospheric extinction profiles measured by lidar. Calculated atmospheric and aerosol heating effects was compared with vertical meteorological parameters measured by radiosonde. The result shows light-absorbing aerosol has the potential to affect the stability of planetary boundary layer.

  1. Absorption Coefficient, Molecular Composition, and Photodegradation of Different Types of Brown Carbon Aerosols

    NASA Astrophysics Data System (ADS)

    Lee, H. J.; Aiona, P. K.; Nizkorodov, S.; Laskin, J.; Laskin, A.

    2014-12-01

    Atmospheric aerosols that absorb solar radiation have a direct effect on climate. Brown carbon (BrC) represents the type of carbonaceous aerosols characterized by large absorption coefficients in the near-UV range of the spectrum. BrC can be either directly emitted into the atmosphere from combustion sources, or be formed in the atmosphere through multi-phase reactions, such as aging of secondary organic aerosols (SOA) mediated by ammonium sulfate (AS). Under the conditions of exposure to solar radiation, both primary and secondary BrC can potentially change their molecular composition and optical properties as a result of photodegradation of chromophoric compounds. This presentation will discuss the molecular level composition, the absorption and fluorescence spectra, and the mechanism of photodegradation among several representative types of BrC. The primary BrC samples include aerosol produced by smoldering wood combustion. The secondary BrC samples include AS aged products of chamber-generated SOA, products of reaction between methylglyoxal and AS, and SOA produced by the hogh-NOx photooxdiation of aromatic compounds, such as naphthalene. This presentation will also include preliminary data on the absorption and fluorescence spectra of photo-degraded bioaerosols. In all cases, absorption spectra of extracted bulk samples are measured during irradiation by a known flux of UV or visible light. The molecular level composition of the fresh and photobleached samples are characterized by high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). Photobleaching of BrC is found to occur over a range of atmospherically relevant time scales. In many cases, the molecular level composition of photobleached BrC exhibits only subtle changes suggesting that the optical and fluorescence properties of BrC are controlled by a few compounds present in low quantities. The observed fluorescence from non-biological BrC indicates potential issues in using fluorescence

  2. Spectral Light Absorption and Scattering by Aerosol Particles in Central Amazonia

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Holanda, B. A.; Ferreira De Brito, J.; Carbone, S.; Barbosa, H. M.; Rizzo, L. V.; Cirino, G. G.; Andreae, M. O.; Saturno, J.; Pöhlker, C.; Martin, S. T.; Holben, B. N.; Schafer, J.

    2015-12-01

    As part of the GoAmazon2014/5, a detailed characterization of spectral light absorption and light scattering was performed at four research sites located in the central Amazon forest at different distances upwind and downwind of Manaus. The sites ATTO (T0a) and Embrapa (T0e) are located upwind of Manaus where it is possible to observe very pristine atmospheric conditions in wet season. The site Tiwa (T2) is being operated under the direct influence of the Manaus plume at 5 km downwind of Manaus and, finally, the Manacapuru (T3) site is located at about 60 km downwind of Manaus. The spectral dependence of light absorption and light scattering were measured using Aethalometers (7-wavelengths) and Nephelometers (3-wavelengths), respectively. By calculating the Absorption Angstrom Exponent (AAE), it was possible to get information about the source of the aerosol whereas the Scattering Angstrom Exponent (SAE) gives information about its size distribution. Sunphotometers from the AERONET network were set up at T3 and T0e sites to measure column Aerosol Optical Depth (AOD). For all the stations, much higher absorption and scattering coefficients were observed during the dry season in comparison to the wet season, as a result of the larger concentration of BC and OC present in the biomass burning events. Additionally, we also observed Manaus plume pollution that alters the BC signal. There is also an increase of the AAE during the dry season due to the larger amount of aerosols from biomass burning compared with urban pollution. High values of AAE are also observed during the wet season, attributed to the presence of long-range transport of aerosols from Africa. The SAE for all the sites are lower during the wet season, with the dominance of large biological particles, and increases during the dry season as a consequence of fine particles emitted from both biomass and fossil fuel burning. The AOD at T0e and T3 (Jan-Jun/2014) showed very similar values ranging from 0.05 to

  3. Influences of external vs. core-shell mixing on aerosol optical properties at various relative humidities.

    PubMed

    Ramachandran, S; Srivastava, Rohit

    2013-05-01

    Aerosol optical properties of external and core-shell mixtures of aerosol species present in the atmosphere are calculated in this study for different relative humidities. Core-shell Mie calculations are performed using the values of radii, refractive indices and densities of aerosol species that act as core and shell, and the core-shell radius ratio. The single scattering albedo (SSA) is higher when the absorbing species (black carbon, BC) is the core, while for a sulfate core SSA does not vary significantly as the BC in the shell dominates the absorption. Absorption gets enhanced in core-shell mixing of absorbing and scattering aerosols when compared to their external mixture. Thus, SSA is significantly lower for a core-shell mixture than their external mixture. SSA is more sensitive to core-shell ratio than mode radius when BC is the core. The extinction coefficient, SSA and asymmetry parameter are higher for external mixing when compared to BC (core)-water soluble aerosol (shell), and water soluble aerosol (core)-BC (shell) mixtures in the relative humidity range of 0 to 90%. Spectral SSA exhibits the behaviour of the species which acts as a shell in core-shell mixing. The asymmetry parameter for an external mixture of water soluble aerosol and BC is higher than BC (core)-water soluble aerosol (shell) mixing and increases as function of relative humidity. The asymmetry parameter for the water soluble aerosol (core)-BC (shell) is independent of relative humidity as BC is hydrophobic. The asymmetry parameter of the core-shell mixture decreases when BC aerosols are involved in mixing, as the asymmetry parameter of BC is lower. Aerosol optical depth (AOD) of core-shell mixtures increases at a higher rate when the relative humidity exceeds 70% in continental clean and urban aerosol models, whereas AOD remains the same when the relative humidity exceeds 50% in maritime aerosol models. The SSA for continental aerosols varies for core-shell mixing of water soluble

  4. A comprehensive climatology of Arctic aerosol properties on the North Slope of Alaska

    NASA Astrophysics Data System (ADS)

    Creamean, Jessie; de Boer, Gijs; Shupe, Matthew; McComiskey, Allison

    2016-04-01

    Evaluating aerosol properties has implications for the formation of Arctic clouds, resulting in impacts on cloud lifetime, precipitation processes, and radiative forcing. There are many remaining uncertainties and large discrepancies regarding modeled and observed Arctic aerosol properties, illustrating the need for more detailed observations to improve simulations of Arctic aerosol and more generally, projections of the components of the aerosol-driven processes that impact sea ice loss/gain. In particular, the sources and climatic effects of Arctic aerosol particles are severely understudied. Here, we present a comprehensive, long-term record of aerosol observations from the North Slope of Alaska baseline site at Barrow. These measurements include sub- and supermicron (up to 10 μm) total mass and number concentrations, sub- and supermicron soluble inorganic and organic ion concentrations, submicron metal concentrations, submicron particle size distributions, and sub- and supermicron absorption and scattering properties. Aerosol extinction and number concentration measurements extend back to 1976, while the remaining measurements were implemented since. Corroboration between the chemical, physical, and optical property measurements is evident during periods of overlapping observations, demonstrating the reliability of the measurements. During the Arctic Haze in the winter/spring, high concentrations of long-range transported submicron sea salt, mineral dust, industrial metals, pollution (non-sea salt sulfate, nitrate, ammonium), and biomass burning species are observed concurrent with higher concentrations of particles with sizes that span the submicron range, enhanced absorption and scattering coefficients, and largest Ångström exponents. The summer is characterized by high concentrations of small biogenic aerosols (< 100 nm) and low extinction coefficients. Fall is characterized by clean conditions, with supermicron sea salt representing the dominant aerosol

  5. Multiwavelength In-Situ Aerosol Scattering and Absorption During the NEAQS-ITCT 2004 Field Campaign: Aerosol Classification, Case Studies, and Data Interpretation

    NASA Astrophysics Data System (ADS)

    Sierau, B.; Covert, D.; Coffman, D.; Quinn, P.; Bates, T.

    2005-12-01

    In-situ, three wavelength measurements of aerosol scattering and absorption of the New York and Boston urban pollution outflow were carried out aboard the NOAA research vessel Ronald H. Brown during the NEAQS-ITCT 2004 (New England Air Quality Study-Intercontinental Transport and Chemical Transformation Study) field campaign during July 2004 in the Gulf of Maine. Aerosol scattering, backscattering and absorption-coefficients were measured using integrating nephelometers and multiwavelength, filter-based absorption photometers (PSAPs) at ~55-60% RH (nephelometers). Two data sets were collected, one for particles with diameters dp<10μm and one for particles <1μm. The purpose of the latter was to focus on the largely pollution related accumulation mode and to minimize the uncertainty due to highly variable near-surface sea salt aerosol. Combining the aerosol scattering and absorption coefficients σsp and σap yields the derived, intensive parameters, single-scattering albedo, ω=σsp/(σsp+σap), Ångström exponents, å, for σsp, and σap, the hemispheric backscattering ratio, and the fine mode fraction of the aerosol, FMF =σsp(dp<1μm)/σsp(dp<10μm). These are key parameters in estimating aerosol direct radiative forcing and they provide constraints on model building and closure studies with physical and chemical aerosol properties. They are important for relating in-situ optical properties to those sensed remotely, e.g., optical depth from ground- or aircraft-based sun photometry or optical depth from satellite, and to the FMF retrieved from satellite data. The measured and derived data will be classified based on a trajectory analysis of the sampled air masses to identify distinct aerosol populations and sources. Case studies describing the aging of pollution plumes are calculated and analyzed in context of other measurements and the prevailing meteorology and the upwind sources. The obtained relationship between in-situ Ångström and FMF will be compared

  6. Optical properties of aerosols at Grand Canyon National Park

    NASA Astrophysics Data System (ADS)

    Malm, William C.; Day, Derek E.

    Visibility in the United States is expected to improve over the next few decades because of reduced emissions, especially sulfur dioxide. In the eastern United States, sulfates make up about 60-70% of aerosol extinction, while in the inner mountain west that fraction is only about 30%. In the inner mountain west, carbon aerosols make up about 35% of extinction, while coarse mass contributes between 15 and 25% depending on how absorption is estimated. Although sulfur dioxide emissions are projected to decrease, carbon emissions due to prescribed fire activity will increase by factors of 5-10, and while optical properties of sulfates have been extensively studied, similar properties of carbon and coarse particles are less well understood. The inability to conclusively apportion about 50% of the extinction budget motivated a study to examine aerosol physio-chemical-optical properties at Grand Canyon, Arizona during the months of July and August. Coarse particle mass has usually been assumed to consist primarily of wind-blown dust, with a mass-scattering efficiency between about 0.4 and 0.6 m 2 g -1. Although there were episodes where crustal material made up most of the coarse mass, on the average, organics and crustal material mass were about equal. Furthermore, about one-half of the sampling periods had coarse-mass-scattering efficiencies greater than 0.6 m 2 g -1 and at times coarse-mass-scattering efficiencies were near 1.0 m 2 g -1. It was shown that absorption by coarse- and fine-particle absorption were about equal and that both fine organic and sulfate mass-scattering efficiencies were substantially less than the nominal values of 4.0 and 3.0 m 2 g -1 that have typically been used.

  7. Radiative Properties of Smoke and Aerosol Over Land Surfaces

    NASA Technical Reports Server (NTRS)

    King, Michael D.

    2000-01-01

    This talk discusses smoke and aerosol's radiative properties with particular attention to distinguishing the measurement over clear sky from clouds over land, sea, snow, etc. surfaces, using MODIS Airborne Simulator data from (Brazil, arctic sea ice and tundra and southern Africa, west Africa, and other ecosystems. This talk also discusses the surface bidirectional reflectance using Cloud Absorption Radiometer, BRDF measurements of Saudi Arabian desert, Persian Gulf, cerrado and rain forests in Brazil, sea ice, tundra, Atlantic Ocean, Great Dismal Swamp, Kuwait oil fire smoke. Recent upgrades to instrument (new TOMS UVA channels at 340 and 380 planned use in Africa (SAFARI 2000) and possibly for MEIDEX will also be discussed. This talk also plans to discuss the spectral variation of surface reflectance over land and the sensitivity of off-nadir view angles to correlation between visible near-infrared reflectance for use in remote sensing of aerosol over land.

  8. Systematic Relationships among Background SE U.S. Aerosol Optical, Micro-physical, and Chemical Properties-Development of an Optically-based Aerosol Characterization

    NASA Astrophysics Data System (ADS)

    Sherman, J. P.; Link, M. F.; Zhou, Y.

    2014-12-01

    Remote sensing-based retrievals of aerosol composition require known or assumed relationships between aerosol optical properties and types. Most optically-based aerosol classification schemes apply some combination of the spectral dependence of aerosol light scattering and absorption-using the absorption and either scattering or extinction Angstrom exponents (AAE, SAE and EAE), along with single-scattering albedo (SSA). These schemes can differentiate between such aerosol types as dust, biomass burning, and urban/industrial but no such studies have been conducted in the SE U.S., where a large fraction of the background aerosol is a variable mixture of biogenic SOA, sulfates, and black carbon. In addition, AERONET retrievals of SSA are often highly uncertain due to low AOD in the region during most months. The high-elevation, semi-rural AppalAIR facility at Appalachian State University in Boone, NC (1090m ASL, 36.210N, 81.690W) is home to the only co-located NOAA-ESRL and AERONET monitoring sites in the eastern U.S. Aerosol chemistry measured at AppalAIR is representative of the background SE U.S (Link et al. 2014) Dried aerosol light absorption and dried and humidified aerosol light scattering and hemispheric backscattering at 3 visible wavelengths and 2 particle size cuts (sub-1μm and sub-10μm) are measured continuously. Measurements of size-resolved, non-refractory sub-1μm aerosol composition were made by a co-located AMS during the 2012-2013 summers and 2013 winter. Systematic relationships among aerosol optical, microphysical, and chemical properties were developed to better understand aerosol sources and processes and for use in higher-dimension aerosol classification schemes. The hygroscopic dependence of visible light scattering is sensitive to the ratio of sulfate to organic aerosol(OA), as are SSA and AAE. SAE is a less sensitive indicator of fine-mode aerosol size than hemispheric backscatter fraction (b) and is more sensitive to fine-mode aerosol

  9. Method and apparatus for aerosol-particle absorption spectroscopy. [DOE patent application

    SciTech Connect

    Campillo, A.J.; Lin, H.B.

    1981-06-25

    A method and apparatus are described for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy. In another embodiment the heating beam passes through an interferometer and the scattered light reflects the Fourier Transform of the absorption spectra.

  10. Background Southeast United States Aerosol Optical Properties and Their Dependence Upon Meteorology

    NASA Astrophysics Data System (ADS)

    Pawlyszyn, C.; West, M.; Sherman, J. P.; Link, M.; Zhou, Y.

    2015-12-01

    Aerosol effects on SE U.S. radiation budget are highly-seasonal. Aerosol loading is much higher in summer, due largely to high levels of biogenic secondary organic aerosol and sulfates. Aerosol loading is lowest in winter. Aerosol optical properties relevant to radiative forcing have been measured continuously at the Appalachian Atmospheric Interdisciplinary Research facility (AppalAIR) since the summer of 2009. AppalAIR is the only site in the eastern US to house co-located NOAA ESRL and NASA AeroNET instrumentation and is located in the mountains of Boone, NC. Lower tropospheric sub-micron (PM1) light scattering and absorption coefficients measured over seven summers and six winters are presented here, in addition to PM1 organic and sulfate aerosol mass concentrations measured during summers 2012-2013 as well as winter 2013. The objective is to determine the influence of aerosol sources and meteorology along the air mass back-trajectories on aerosol loading and composition. PM1 aerosol mass was dominated by organic aerosol and sulfate during the periods measured. Aerosol light scattering and organic aerosol concentrations were positively correlated during summer with temperature and solar flux along the parcel back-trajectory and negatively-correlated with rainfall along the back-trajectory. Wet deposition was a major factor in the difference between the upper and lower scattering coefficient quartiles for both summer and winter. Summer PM1 light scattering coefficient declined by approximately 30-40% since 2009, with smaller decreases during winter months. Long-term studies of aerosol optical properties from the regionally-representative AppalAIR site are necessary to determine the relationships between changing SE U.S. air quality and aerosol effects on regional climate and weather.

  11. Aerosol particle absorption spectroscopy by photothermal modulation of Mie scattered light

    SciTech Connect

    Campillo, A.J.; Dodge, C.J.; Lin, H.B.

    1981-09-15

    Absorption spectroscopy of suspended submicron-sized aqueous ammonium-sulfate aerosol droplets has been performed by employing a CO/sub 2/ laser to photothermally modulate visible Mie scattered light. (AIP)

  12. Optical Properties and Aging of Light Absorbing Secondary Organic Aerosol

    SciTech Connect

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; Laskin, Julia; Kathmann, Shawn M.; Wise, Matthew E.; Caylor, Ryan; Imholt, Felisha; Selimovic, Vanessa; Shilling, John E.

    2016-10-14

    The light-absorbing organic aerosol (OA), commonly referred to as “brown carbon (BrC)”, has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various VOC precursors, NOx concentrations, photolysis time and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficients (MAC) value is observed from toluene SOA products formed under high NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organonitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible and UV light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed-SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.

  13. Use of the NASA GEOS-5 SEAC4RS Meteorological and Aerosol Reanalysis for assessing simulated aerosol optical properties as a function of smoke age

    NASA Astrophysics Data System (ADS)

    Randles, C. A.; da Silva, A. M., Jr.; Colarco, P. R.; Darmenov, A.; Buchard, V.; Govindaraju, R.; Chen, G.; Hair, J. W.; Russell, P. B.; Shinozuka, Y.; Wagner, N.; Lack, D.

    2014-12-01

    The NASA Goddard Earth Observing System version 5 (GEOS-5) Earth system model, which includes an online aerosol module, provided chemical and weather forecasts during the SEAC4RS field campaign. For post-mission analysis, we have produced a high resolution (25 km) meteorological and aerosol reanalysis for the entire campaign period. In addition to the full meteorological observing system used for routine NWP, we assimilate 550 nm aerosol optical depth (AOD) derived from MODIS (both Aqua and Terra satellites), ground-based AERONET sun photometers, and the MISR instrument (over bright surfaces only). Daily biomass burning emissions of CO, CO2, SO2, and aerosols are derived from MODIS fire radiative power retrievals. We have also introduced novel smoke "age" tracers, which provide, for a given time, a snapshot histogram of the age of simulated smoke aerosol. Because GEOS-5 assimilates remotely sensed AOD data, it generally reproduces observed (column) AOD compared to, for example, the airborne 4-STAR instrument. Constraining AOD, however, does not imply a good representation of either the vertical profile or the aerosol microphysical properties (e.g., composition, absorption). We do find a reasonable vertical structure for aerosols is attained in the model, provided actual smoke injection heights are not much above the planetary boundary layer, as verified with observations from DIAL/HRSL aboard the DC8. The translation of the simulated aerosol microphysical properties to total column AOD, needed in the aerosol assimilation step, is based on prescribed mass extinction efficiencies that depend on wavelength, composition, and relative humidity. Here we also evaluate the performance of the simulated aerosol speciation by examining in situ retrievals of aerosol absorption/single scattering albedo and scattering growth factor (f(RH)) from the LARGE and AOP suite of instruments. Putting these comparisons in the context of smoke age as diagnosed by the model helps us to

  14. Aerosol Characterization and New Instrumentation for Better Understanding Snow Radiative Properties

    NASA Astrophysics Data System (ADS)

    Beres, N. D.

    2015-12-01

    Snow albedo is determined by snowpack thickness and grain size, but also affected by contamination with light-absorbing, microscopic (e.g., mineral dust, combustion aerosols, bio-aerosols) and macroscopic (e.g., microalgae, plant debris, sand, organisms) compounds. Most currently available instruments for measuring snow albedo utilize the natural, downward flux of solar radiation and the reflected upward flux. This reliance on solar radiation (and, thus, large zenith angles and clear-sky conditions) leads to severe constraints, preventing characterization of detailed diurnal snow albedo cycles. Here, we describe instrumentation and methodologies to address these limitations with the development and deployment of new snow radiation sensors for measuring surface spectral and in-snow radiative properties. This novel instrumentation will be tested at the CRREL/UCSB Eastern Sierra (CUES) Snow Study Site at Mammoth Mountain, which is extensively instrumented for characterizing snow properties including snow albedo and surface morphology. However, it has been lacking instrumentation for the characterization of aerosols that can be deposited on the snow surface through dry and wet deposition. Currently, we are installing aerosol instrumentation at the CUES site, which are also described. This includes instruments for the multi-wavelength measurement of aerosol scattering and absorption coefficients and for the characterization of aerosol size distribution. Knowledge of aerosol concentration and physical and optical properties will allow for the study of aerosol deposition and modification of snow albedo and for establishing an aerosol climatology for the CUES site.

  15. Midinfrared optical properties of petroleum oil aerosols

    NASA Astrophysics Data System (ADS)

    Gurton, K. P.; Bruce, C. W.

    1994-08-01

    The mass normalized absorption and extinction coefficients were measured for fog oil aerosol at 3.4 micrometers with a combined photoacoustic and transmissometer system. An extinction spectral profile was determined over a range of infrared (IR) wavelengths from 2.7 to 4.0 micrometers by an IR scanning transmissometer. The extinction spectrum was mass normalized by referencing it to the photoacoustic portion of the experiment. A corresponding Mie calculation was conducted and compared with the above measurements. Agreement is good for the most recent optical coefficients. An extrapolation of this data to other similar petroleum products such as kerosene or diesel fuel that exhibit similar bulk absorption characteristics were briefly examined.

  16. Effects of morphology on the radiative properties of internally mixed light absorbing carbon aerosols with different aging status.

    PubMed

    Cheng, Tianhai; Wu, Yu; Chen, Hao

    2014-06-30

    Light absorbing carbon aerosols play a substantial role in climate change through radiative forcing, which is the dominant absorber of solar radiation. Radiative properties of light absorbing carbon aerosols are strongly dependent on the morphological factors and the mixing mechanism of black carbon with other aerosol components. This study focuses on the morphological effects on the optical properties of internally mixed light absorbing carbon aerosols using the numerically exact superposition T-matrix method. Three types aerosols with different aging status such as freshly emitted BC particles, thinly coated light absorbing carbon aerosols, heavily coated light absorbing carbon aerosols are studied. Our study showed that morphological factors change with the aging of internally mixed light absorbing carbon aerosols to result in a dramatic change in their optical properties. The absorption properties of light absorbing carbon aerosols can be enhanced approximately a factor of 2 at 0.67 um, and these enhancements depend on the morphological factors. A larger shell/core diameter ratio of volume-equivalent shell-core spheres (S/C), which indicates the degree of coating, leads to stronger absorption. The enhancement of absorption properties accompanies a greater enhancement of scattering properties, which is reflected in an increase in single scattering albedo (SSA). The enhancement of single scattering albedo due to the morphological effects can reach a factor of 3.75 at 0.67 μm. The asymmetry parameter has a similar yet smaller enhancement. Moreover, the corresponding optical properties of shell-and-core model determined by using Lorenz -Mie solutions are presented for comparison. We found that the optical properties of internally mixed light absorbing carbon aerosol can differ fundamentally from those calculated for the Mie theory shell-and-core model, particularly for thinly coated light absorbing carbon aerosols. Our studies indicate that the complex morphology

  17. The impact of biogenic carbon emissions on aerosol absorption inMexico City

    SciTech Connect

    Marley, N; Gaffney, J; Tackett, M J; Sturchio, N; Hearty, L; Martinez, N; Hardy, K D; Machany-Rivera, A; Guilderson, T P; MacMillan, A; Steelman, K

    2009-02-24

    In order to determine the wavelength dependence of atmospheric aerosol absorption in the Mexico City area, the absorption angstrom exponents (AAEs) were calculated from aerosol absorption measurements at seven wavelengths obtained with a seven-channel aethalometer during two field campaigns, the Mexico City Metropolitan Area study in April 2003 (MCMA 2003) and the Megacity Initiative: Local and Global Research Observations in March 2006 (MILAGRO). The AAEs varied from 0.76 to 1.56 in 2003 and from 0.54 to 1.52 in 2006. The AAE values determined in the afternoon were consistently higher than the corresponding morning values, suggesting the photochemical formation of absorbing secondary organic aerosols (SOA) in the afternoon. The AAE values were compared to stable and radiocarbon isotopic measurements of aerosol samples collected at the same time to determine the sources of the aerosol carbon. The fraction of modern carbon (fM) in the aerosol samples, as determined from {sup 14}C analysis, showed that 70% of the carbonaceous aerosols in Mexico City were from modern sources, indicating a significant impact from biomass burning during both field campaigns. The {sup 13}C/{sup 12}C ratios of the aerosol samples illustrate the significant impact of Yucatan forest fires (C-3 plants) in 2003 and local grass fires (C-4 plants) at site T1 in 2006. A direct comparison of the fM values, stable carbon isotope ratios, and calculated aerosol AAEs suggested that the wavelength dependence of the aerosol absorption was controlled by the biogenically derived aerosol components.

  18. Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: sparse methods for statistical selection of relevant absorption bands

    NASA Astrophysics Data System (ADS)

    Takahama, Satoshi; Ruggeri, Giulia; Dillner, Ann M.

    2016-07-01

    Various vibrational modes present in molecular mixtures of laboratory and atmospheric aerosols give rise to complex Fourier transform infrared (FT-IR) absorption spectra. Such spectra can be chemically informative, but they often require sophisticated algorithms for quantitative characterization of aerosol composition. Naïve statistical calibration models developed for quantification employ the full suite of wavenumbers available from a set of spectra, leading to loss of mechanistic interpretation between chemical composition and the resulting changes in absorption patterns that underpin their predictive capability. Using sparse representations of the same set of spectra, alternative calibration models can be built in which only a select group of absorption bands are used to make quantitative prediction of various aerosol properties. Such models are desirable as they allow us to relate predicted properties to their underlying molecular structure. In this work, we present an evaluation of four algorithms for achieving sparsity in FT-IR spectroscopy calibration models. Sparse calibration models exclude unnecessary wavenumbers from infrared spectra during the model building process, permitting identification and evaluation of the most relevant vibrational modes of molecules in complex aerosol mixtures required to make quantitative predictions of various measures of aerosol composition. We study two types of models: one which predicts alcohol COH, carboxylic COH, alkane CH, and carbonyl CO functional group (FG) abundances in ambient samples based on laboratory calibration standards and another which predicts thermal optical reflectance (TOR) organic carbon (OC) and elemental carbon (EC) mass in new ambient samples by direct calibration of infrared spectra to a set of ambient samples reserved for calibration. We describe the development and selection of each calibration model and evaluate the effect of sparsity on prediction performance. Finally, we ascribe

  19. AeroCom INSITU Project: Comparison of Aerosol Optical Properties from In-situ Surface Measurements and Model Simulations

    NASA Astrophysics Data System (ADS)

    Schmeisser, L.; Andrews, E.; Schulz, M.; Fiebig, M.; Zhang, K.; Randles, C. A.; Myhre, G.; Chin, M.; Stier, P.; Takemura, T.; Krol, M. C.; Bian, H.; Skeie, R. B.; da Silva, A. M., Jr.; Kokkola, H.; Laakso, A.; Ghan, S.; Easter, R. C.

    2015-12-01

    AeroCom, an open international collaboration of scientists seeking to improve global aerosol models, recently initiated a project comparing model output to in-situ, surface-based measurements of aerosol optical properties. The model/measurement comparison project, called INSITU, aims to evaluate the performance of a suite of AeroCom aerosol models with site-specific observational data in order to inform iterative improvements to model aerosol modules. Surface in-situ data have the unique property of being traceable to physical standards, which is a big asset in accomplishing the overarching goal of bettering the accuracy of aerosol processes and predicative capability of global climate models. The INSITU project looks at how well models reproduce aerosol climatologies on a variety of time scales, aerosol characteristics and behaviors (e.g., aerosol persistence and the systematic relationships between aerosol optical properties), and aerosol trends. Though INSITU is a multi-year endeavor, preliminary phases of the analysis, using GOCART and other models participating in this AeroCom project, show substantial model biases in absorption and scattering coefficients compared to surface measurements, though the sign and magnitude of the bias varies with location and optical property. Spatial patterns in the biases highlight model weaknesses, e.g., the inability of models to properly simulate aerosol characteristics at sites with complex topography (see Figure 1). Additionally, differences in modeled and measured systematic variability of aerosol optical properties suggest that some models are not accurately capturing specific aerosol co-dependencies, for example, the tendency of in-situ surface single scattering albedo to decrease with decreasing aerosol extinction coefficient. This study elucidates specific problems with current aerosol models and suggests additional model runs and perturbations that could further evaluate the discrepancies between measured and modeled

  20. Vertical distribution of aerosol optical properties based on aircraft measurements over the Loess Plateau in China.

    PubMed

    Li, Junxia; Liu, Xingang; Yuan, Liang; Yin, Yan; Li, Zhanqing; Li, Peiren; Ren, Gang; Jin, Lijun; Li, Runjun; Dong, Zipeng; Li, Yiyu; Yang, Junmei

    2015-08-01

    Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients (σsc), absorption coefficients (σab), Angström exponent (α), single scattering albedo (ω), backscattering ratio (βsc), aerosol mass scattering proficiency (Qsc) and aerosol surface scattering proficiency (Qsc(')) were obtained. The mean statistical values of σsc were 77.45 Mm(-1) (at 450 nm), 50.72 Mm(-1) (at 550n m), and 32.02 Mm(-1) (at 700 nm). The mean value of σab was 7.62 Mm(-1) (at 550 nm). The mean values of α, βsc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters (ED) of aerosols were less than 0.8 μm. The vertical profiles of σsc,, α, βsc, Qsc and Qsc(') showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and βsc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σsc, α, βsc, Qsc, Qsc('), σab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions.

  1. Influence of the vertical absorption profile of mixed Asian dust plumes on aerosol direct radiative forcing over East Asia

    NASA Astrophysics Data System (ADS)

    Noh, Young Min; Lee, Kwonho; Kim, Kwanchul; Shin, Sung-Kyun; Müller, Detlef; Shin, Dong Ho

    2016-08-01

    We estimate the aerosol direct radiative forcing (ADRF) and heating rate profiles of mixed East Asian dust plumes in the solar wavelength region ranging from 0.25 to 4.0 μm using the Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART) code. Vertical profiles of aerosol extinction coefficients and single-scattering albedos (SSA) were derived from measurements with a multi-wavelength Raman lidar system. The data are used as input parameters for our radiative transfer calculations. We considered four cases of radiative forcing in SBDART: 1. dust, 2. pollution, 3. mixed dust plume and the use of vertical profiles of SSA, and 4. mixed dust plumes and the use of column-averaged values of SSA. In our sensitivity study we examined the influence of SSA and aerosol layer height on our results. The ADRF at the surface and in the atmosphere shows a small dependence on the specific shape of the aerosol extinction vertical profile and its light-absorption property for all four cases. In contrast, at the top of the atmosphere (TOA), the ADRF is largely affected by the vertical distribution of the aerosols extinction. This effect increases if the light-absorption capacity (decrease of SSA) of the aerosols increases. We find different radiative effects in situations in which two layers of aerosols had different light-absorption properties. The largest difference was observed at the TOA for an absorbing aerosol layer at high altitude in which we considered in one case the vertical profile of SSA and in another case the column-averaged SSA only. The ADRF at the TOA increases when the light-absorbing aerosol layer is located above 3 km altitude. The differences between height-resolved SSA, which can be obtained from lidar data, and total layer-mean SSA indicates that the use of a layer-mean SSA can be rather misleading as it can induce a large error in the calculation of the ADRF at the TOA, which in turn may cause errors in the vertical profiles of heating rates.

  2. Climatological Aspects of the Optical Properties of Fine/Coarse Mode Aerosol Mixtures

    NASA Technical Reports Server (NTRS)

    Eck, T. F.; Holben, B. N.; Sinyuk, A.; Pinker, R. T.; Goloub, P.; Chen, H.; Chatenet, B.; Li, Z.; Singh, R. P.; Tripathi, S.N.; Reid, J. S.; Giles, D. M.; Dubovik O.; O'Neill, N. T.; Smirnov, A.; Wang, P.; Xia, X.

    2010-01-01

    Aerosol mixtures composed of coarse mode desert dust combined with fine mode combustion generated aerosols (from fossil fuel and biomass burning sources) were investigated at three locations that are in and/or downwind of major global aerosol emission source regions. Multiyear monitoring data at Aerosol Robotic Network sites in Beijing (central eastern China), Kanpur (Indo-Gangetic Plain, northern India), and Ilorin (Nigeria, Sudanian zone of West Africa) were utilized to study the climatological characteristics of aerosol optical properties. Multiyear climatological averages of spectral single scattering albedo (SSA) versus fine mode fraction (FMF) of aerosol optical depth at 675 nm at all three sites exhibited relatively linear trends up to 50% FMF. This suggests the possibility that external linear mixing of both fine and coarse mode components (weighted by FMF) dominates the SSA variation, where the SSA of each component remains relatively constant for this range of FMF only. However, it is likely that a combination of other factors is also involved in determining the dynamics of SSA as a function of FMF, such as fine mode particles adhering to coarse mode dust. The spectral variation of the climatological averaged aerosol absorption optical depth (AAOD) was nearly linear in logarithmic coordinates over the wavelength range of 440-870 nm for both the Kanpur and Ilorin sites. However, at two sites in China (Beijing and Xianghe), a distinct nonlinearity in spectral AAOD in logarithmic space was observed, suggesting the possibility of anomalously strong absorption in coarse mode aerosols increasing the 870 nm AAOD.

  3. Impact of Nonabsorbing Anthropogenic Aerosols on Clear-Sky Atmospheric Absorption

    NASA Technical Reports Server (NTRS)

    Stier, Philip; Seinfeld, John H.; Kinne, Stefan; Feichter,Johann; Boucher, Olivier

    2006-01-01

    Absorption of solar radiation by atmospheric aerosol has become recognized as important in regional and global climate. Nonabsorbing, hydrophilic aerosols, such as sulfate, potentially affect atmospheric absorption in opposing ways: first, decreasing absorption through aging initially hydrophobic black carbon (BC) to a hydrophilic state, enhancing its removal by wet scavenging, and consequently decreasing BC lifetime and abundance, and second, increasing absorption through enhancement of the BC absorption efficiency by internal mixing as well as through increasing the amount of diffuse solar radiation in the atmosphere. On the basis of General Circulation Model studies with an embedded microphysical aerosol module we systematically demonstrate the significance of these mechanisms both on the global and regional scales. In remote transport regions, the first mechanism prevails, reducing atmospheric absorption, whereas in the vicinity of source regions, despite enhanced wet scavenging, absorption is enhanced owing to the prevalence of the second mechanisms. Our findings imply that the sulfur to BC emission ratio plays a key role in aerosol absorption.

  4. Global aerosol optical properties and application to Moderate Resolution Imaging Spectroradiometer aerosol retrieval over land

    NASA Astrophysics Data System (ADS)

    Levy, Robert C.; Remer, Lorraine A.; Dubovik, Oleg

    2007-07-01

    As more information about global aerosol properties has become available from remotely sensed retrievals and in situ measurements, it is prudent to evaluate this new information, both on its own and in the context of satellite retrieval algorithms. Using the climatology of almucantur retrievals from global Aerosol Robotic Network (AERONET) Sun photometer sites, we perform cluster analysis to determine aerosol type as a function of location and season. We find that three spherical-derived types (describing fine-sized dominated aerosol) and one spheroid-derived types (describing coarse-sized dominated aerosol, presumably dust) generally describe the range of AERONET observed global aerosol properties. The fine-dominated types are separated mainly by their single scattering albedo (ω0), ranging from nonabsorbing aerosol (ω0 ˜ 0.95) in developed urban/industrial regions, to moderately absorbing aerosol (ω0 ˜ 0.90) in forest fire burning and developing industrial regions, to absorbing aerosol (ω0 ˜ 0.85) in regions of savanna/grassland burning. We identify the dominant aerosol type at each site, and extrapolate to create seasonal 1° × 1° maps of expected aerosol types. Each aerosol type is bilognormal, with dynamic (function of optical depth) size parameters (radius, standard deviation, volume distribution) and complex refractive index. Not only are these parameters interesting in their own right, they can also be applied to aerosol retrieval algorithms, such as to aerosol retrieval over land from Moderate Resolution Imaging Spectroradiometer. Independent direct-Sun AERONET observations of spectral aerosol optical depth (τ) are consistent the spectral dependence of the models, indicating that our derived aerosol models are relevant.

  5. Morphology and Optical Properties of Mixed Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Fard, Mehrnoush M.; Krieger, Ulrich; Rudich, Yinon; Marcolli, Claudia; Peter, Thomas

    2016-04-01

    Experiments and modeling studies have shown that deliquesced aerosols can exist not only as one-phase system containing organics, inorganic salts and water, but often as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase (1,2). Recent laboratory studies conducted with model mixtures representing tropospheric aerosols (1,2,3), secondary organic aerosol (SOA) from smog chamber experiments (4), and field measurements (5) suggest that liquid-liquid phase separations (LLPS) is indeed a common phenomenon in mixed organic/ inorganic particles. During LLPS, particles may adopt different morphologies mainly core-shell and partially engulfed. A core-shell configuration will have consequences for heterogeneous chemistry and hygroscopicity and as a result will alter the optical properties of the particles in particular for organic phases containing absorbing molecules, e.g. brown carbon. The primary objective of this project is to establish a method for investigating the morphology of mixed inorganic and absorbing organic compounds of atmospheric relevance and study their radiative properties before, during, and after phase transitions mainly during LLPS. This will be the first study looking into the radiative effect of LLPS in detail. Our ternary model system consist of ammonium sulfate (AS)/ Polyethylene Glycol (PEG)/ and water (H2O). Carminic acid (CA) was added as a proxy for an absorbing organic compound to the system. The behavior of single droplets of above ternary mixture was monitored during relative humidity (RH) cycles using optical microscopy. The same ternary mixture particle was levitated in an electrodynamic balance (EDB) and the change in its absorption properties was measured at varying RH. In addition, Mie-code modeling is used to predict the absorption efficiency of the same ternary system and the result will be compared with the data obtained from EDB experiment. We also intend to determine the occurrence of

  6. Improved aerosol radiative properties as a foundation for solar geoengineering risk assessment

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Keith, D. W.; Keutsch, F. N.

    2016-07-01

    Side effects resulting from the deliberate injection of sulfate aerosols intended to partially offset climate change have motivated the investigation of alternatives, including solid aerosol materials. Sulfate aerosols warm the tropical tropopause layer, increasing the flux of water vapor into the stratosphere, accelerating ozone loss, and increasing radiative forcing. The high refractive index of some solid materials may lead to reduction in these risks. We present a new analysis of the scattering efficiency and absorption of a range of candidate solid aerosols. We utilize a comprehensive radiative transfer model driven by updated, physically consistent estimates of optical properties. We compute the potential increase in stratospheric water vapor and associated longwave radiative forcing. We find that the stratospheric heating calculated in this analysis indicates some materials to be substantially riskier than previous work. We also find that there are Earth-abundant materials that may reduce some principal known risks relative to sulfate aerosols.

  7. Toward Creating A Global Retrospective Climatology of Aerosol Properties

    NASA Technical Reports Server (NTRS)

    Curran, Robert J.; Mishchenko, Michael I.; Hansen, James E. (Technical Monitor)

    2000-01-01

    Tropospheric aerosols are thought to cause a significant direct and indirect climate forcing, but the magnitude of this forcing remains highly uncertain because of poor knowledge of global aerosol characteristics and their temporal changes. The standard long-term global product, the one-channel Advanced Very-High-Resolution Radiometer (AVHRR) aerosol optical thickness over the ocean, relies on a single predefined aerosol model and can be inaccurate in many cases. Furthermore, it provides no information on aerosol column number density, thus making it impossible to estimate the indirect aerosol effect on climate. Total Ozone Mapping Spectrometer (TOMS) data can be used to detect absorbing aerosols over land, but are insensitive to aerosols located below one kilometer. It is thus clear that innovative approaches must be employed in order to extract a more quantitative and accurate aerosol climatology from available satellite and other measurements, thus enabling more reliable estimates of the direct and indirect aerosol forcings. The Global Aerosol Climatology Project (GACP) was established in 1998 as part of the Global Energy and Water Cycle Experiment (GEWEX). Its main objective is to analyze satellite radiance measurements and field observations to infer the global distribution of aerosols, their properties, and their seasonal and interannual variations. The overall goal is to develop advanced global aerosol climatologies for the period of satellite data and to make the aerosol climatologies broadly available through the GACP web site.

  8. Aerosol optical and microphysical properties from POLDER-PARASOL multi-angle photo-polarimetric measurements

    NASA Astrophysics Data System (ADS)

    Hasekamp, O.; Litvinov, P.; Butz, A.

    2010-12-01

    The large uncertainty on the aerosol effects on clouds and climate is reflected in considerable discrepancies between different model simulations of the radiative forcing caused by these effects. Also, there exist even larger differences between values for radiative forcing calculated by models and those estimated from satellites (and model calculations constrained by satellite measurements). Relationships between aerosols and clouds derived from satellite measurements are subject to a number of important limitations. First of all, with current satellite aerosol products it is hard to determine which fraction of the aerosols is anthropogenic and which fraction is natural. Often the rather crude assumption is used that the fine mode contribution is fully anthropogenic. Furthermore, most aerosol types are strongly hygroscopic, which means that in an environment with high relative humidity (in the surrounding of clouds) the particle size increases considerably leading, in turn, to an increase in optical thickness. This effect may be misinterpreted as an apparent relation between aerosol concentration and cloud cover. Also, meteorology effects can be misinterpreted as apparent aerosol-cloud relationships. Accurate information on aerosol size and refractive index (related to chemical composition of aerosols and absorption) is needed to distinguish between natural and anthropogenic aerosols and to distinguish between aerosol effects on cloud formation and apparent relationships due to humidity and meteorology effects. Multi-angle photopolarimetric measurements have the potential to provide the necessary information on these aerosol properties. The POLDER instrument onboard the PARASOL micro-satellite is the only instrument currently in space that performs multi-angle photopolarimetric measurements. To fully exploit the information contained in these measurements a new type of retrieval algorithm is needed that retrieves detailed information on aerosol microphysical and

  9. Measurement of Transport Properties of Aerosolized Nanomaterials

    PubMed Central

    Ku, Bon Ki; Kulkarni, Pramod

    2015-01-01

    Airborne engineered nanomaterials such as single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), functionalized MWCNT, graphene, fullerene, silver and gold nanorods were characterized using a tandem system of a differential mobility analyzer and an aerosol particle mass analyzer to obtain their airborne transport properties and understand their relationship to morphological characteristics. These nanomaterials were aerosolized using different generation methods such as electrospray, pneumatic atomization, and dry aerosolization techniques, and their airborne transport properties such as mobility and aerodynamic diameters, mass scaling exponent, dynamic shape factor, and effective density were obtained. Laboratory experiments were conducted to directly measure mobility diameter and mass of the airborne nanomaterials using tandem mobility-mass measurements. Mass scaling exponents, aerodynamic diameters, dynamic shape factors and effective densities of mobility-classified particles were obtained from particle mass and the mobility diameter. Microscopy analysis using Transmission Electron Microscopy (TEM) was performed to obtain morphological descriptors such as envelop diameter, open area, aspect ratio, and projected area diameter. The morphological information from the TEM was compared with measured aerodynamic and mobility diameters of the particles. The results showed that aerodynamic diameter is smaller than mobility diameter below 500 nm by a factor of 2 to 4 for all nanomaterials except silver and gold nanorods. Morphologies of MWCNTs generated by liquid-based method, such as pneumatic atomization, are more compact than those of dry dispersed MWCNTs, indicating that the morphology depends on particle generation method. TEM analysis showed that projected area diameter of MWCNTs appears to be in reasonable agreement with mobility diameter in the size range from 100 – 400 nm. Principal component analysis of the obtained airborne particle

  10. Characterization of aerosol events based on the column integrated optical aerosol properties and polarimetric measurements

    NASA Astrophysics Data System (ADS)

    Mandija, Florian; Markowicz, Krzysztof; Zawadzka, Olga

    2016-12-01

    Aerosol optical properties are very useful tools for analyzing their radiative effects, which are directly or indirectly related to the global radiation budget. Investigation of column-integrated aerosol optical properties is a worldwide and well-accepted method. The introduction of new methodologies, like those of operation with polarimetric measurements, represent a new challenge to interpret the measurement data and give more detailed information about the aerosol events and their characteristics. Aerosol optical properties during the period June - August 2015 in AERONET Strzyzow station in Poland were analyzed. The aerosol properties like aerosol optical depth, Ångström exponent, fine mode fraction, fine mode contribution on AOD, asymmetry parameter, single scattering angle are analyzed synergistically with the polarimetric measurements of the degree of polarization in different solar zenith and zenith viewing angles at several wavelengths. The overall results show that aerosol events in Strzyzow were characterized mostly by fine mode aerosols. Backward-trajectories suggest that the majority of air masses come from the west. The principal component of the aerosol load was urban/industrial contamination, especially from the inner part of the continent. Additionally, the maximal values of the degree of linear polarization were found to be dependent on the solar zenith and zenith viewing angles and aerosol optical properties like aerosol optical depth and Ångström exponent. These dependencies were further analyzed in a specific case with very high mean values of AOD500 (0.59) and AE440-870 (1.91). The diurnal variations of aerosol optical properties investigated during this special case, suggest that biomass burning products are the main cause of that aerosol load over the stations.

  11. Aerosol properties and associated radiative effects over Cairo (Egypt)

    NASA Astrophysics Data System (ADS)

    El-Metwally, M.; Alfaro, S. C.; Wahab, M. M. Abdel; Favez, O.; Mohamed, Z.; Chatenet, B.

    2011-02-01

    Cairo is one of the largest megacities in the World and the particle load of its atmosphere is known to be particularly important. In this work we aim at assessing the temporal variability of the aerosol's characteristics and the magnitude of its impacts on the transfer of solar radiation. For this we use the level 2 quality assured products obtained by inversion of the instantaneous AERONET sunphotometer measurements performed in Cairo during the Cairo Aerosol CHaracterization Experiment (CACHE), which lasted from the end of October 2004 to the end of March 2006. The analysis of the temporal variation of the aerosol's optical depth (AOD) and spectral dependence suggests that the aerosol is generally a mixture of at least 3 main components differing in composition and size. This is confirmed by the detailed analysis of the monthly-averaged size distributions and associated optical properties (single scattering albedo and asymmetry parameter). The components of the aerosol are found to be 1) a highly absorbing background aerosol produced by daily activities (traffic, industry), 2) an additional, 'pollution' component produced by the burning of agricultural wastes in the Nile delta, and 3) a coarse desert dust component. In July, an enhancement of the accumulation mode is observed due to the atmospheric stability favoring its building up and possibly to secondary aerosols being produced by active photochemistry. More generally, the time variability of the aerosol's characteristics is due to the combined effects of meteorological factors and seasonal production processes. Because of the large values of the AOD achieved during the desert dust and biomass burning episodes, the instantaneous aerosol radiative forcing (RF) at both the top (TOA) and bottom (BOA) of the atmosphere is maximal during these events. For instance, during the desert dust storm of April 8, 2005 RF BOA, RF TOA, and the corresponding atmospheric heating rate peaked at - 161.7 W/m 2, - 65.8 W/m 2

  12. The single scattering properties of the aerosol particles as aggregated spheres

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Gu, X.; Cheng, T.; Xie, D.; Yu, T.; Chen, H.; Guo, J.

    2012-08-01

    The light scattering and absorption properties of anthropogenic aerosol particles such as soot aggregates are complicated in the temporal and spatial distribution, which introduce uncertainty of radiative forcing on global climate change. In order to study the single scattering properties of anthorpogenic aerosol particles, the structures of these aerosols such as soot paticles and soot-containing mixtures with the sulfate or organic matter, are simulated using the parallel diffusion limited aggregation algorithm (DLA) based on the transmission electron microscope images (TEM). Then, the single scattering properties of randomly oriented aerosols, such as scattering matrix, single scattering albedo (SSA), and asymmetry parameter (AP), are computed using the superposition T-matrix method. The comparisons of the single scattering properties of these specific types of clusters with different morphological and chemical factors such as fractal parameters, aspect ratio, monomer radius, mixture mode and refractive index, indicate that these different impact factors can respectively generate the significant influences on the single scattering properties of these aerosols. The results show that aspect ratio of circumscribed shape has relatively small effect on single scattering properties, for both differences of SSA and AP are less than 0.1. However, mixture modes of soot clusters with larger sulfate particles have remarkably important effects on the scattering and absorption properties of aggregated spheres, and SSA of those soot-containing mixtures are increased in proportion to the ratio of larger weakly absorbing attachments. Therefore, these complex aerosols come from man made pollution cannot be neglected in the aerosol retrievals. The study of the single scattering properties on these kinds of aggregated spheres is important and helpful in remote sensing observations and atmospheric radiation balance computations.

  13. North Atlantic Aerosol Radiative Impacts Based on Satellite Measurements and Aerosol Intensive Properties from TARFOX and ACE-2

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Bergstrom, Robert W.; Schmid, B.; Livingston, J. M.

    2000-01-01

    We estimate the impact of North Atlantic aerosols on the net short-wave flux at the tropopause by combining satellite-derived aerosol optical depth (AOD) maps with model aerosol properties determined via closure analyses in TARFOX and ACE 2. We exclude African dust, primarily by restricting latitudes to 25-60 N. The analyses use in situ aerosol composition measurements and air- and ship-borne sun-photometer measurements of AOD spectra. The aerosol model yields computed flux sensitivities (dFlux/dAOD) that agree with measurements by airborne flux radiometers in TARFOX. Its midvisible single-scattering albedo is 0.9. which is in the range obtained from in situ measurements of scattering and absorption in both TARFOX and ACE 2. Combining satellite-derived AOD maps with the aerosol model yields maps of 24-hour average net radiative flux changes. For simultaneous AVHRR, radiance measurements exceeded the sunphotometer AODs by about 0.04. However. shipboard sunphotometer and AVHRR AODs agreed Within 0.02 for data acquired during satellite overflights on two other days. We discuss attempts to demonstrate column closure within the MBL by comparing shipboard sunphotometer AODs and values calculated from simultaneous shipboard in-situ aerosol size distribution measurements. These comparisons were mostly unsuccessful, but they illustrate the difficulties inherent in this type of closure analysis. Specifically, AODs derived from near-surface in-situ size distribution measurements are extremely sensitive to the assumed hygroscopic growth model that itself requires an assumption of particle composition as a function of height and size, to the radiosonde-measured relative humidity, and to the vertical profile of particle number. We investigate further the effects of hygroscopic particle growth within the MBL by using shipboard lidar aerosol backscatter profiles together with the sunphotometer AOD.

  14. Light Absorption of Brown Carbon Aerosol in the Pearl River Delta Region of China

    NASA Astrophysics Data System (ADS)

    Huang, X.

    2015-12-01

    X.F. Huang, J.F. Yuan, L.M. Cao, J. Cui, C.N. Huang, Z.J. Lan and L.Y. He Key Laboratory for Urban Habitat Environmental Science and Technology, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, ChinaCorresponding author. Tel.: +86 755 26032532; fax: +86 755 26035332. E-mail address: huangxf@pku.edu.cn (X. F. Huang). Abstract: The strong spectral dependence of light absorption of brown carbon (BrC) aerosol has been recognized in recent decades. The Absorption Angstrom Exponent (AAE) of ambient aerosol was widely used in previous studies to attribute light absorption of brown carbon at shorter wavelengths, with a theoretical assumption that the AAE of black carbon (BC) aerosol equals to unit. In this study, the AAE method was improved by statistical extrapolation based on ambient measurements in the polluted seasons in typical urban and rural areas in the Pearl River Delta (PRD) region of China. A three-wavelength photoacoustic soot spectrometer (PASS-3) and an aerosol mass spectrometer (AMS) were used to explore the relationship between the ambient measured AAE and the ratio of organic aerosol to BC aerosol, in order to extract the more realistic AAE by pure BC aerosol, which were found to be 0.86, 0.82 and 1.02 at 405nm and 0.70, 0.71, and 0.86 at 532nm in the campaigns of urban-winter, urban-fall, and rural-fall, respectively. Roadway tunnel experiment results further supported the effectiveness of the obtained AAE for pure BC aerosol. In addition, biomass burning experiments proved higher spectral dependence of more-BrC environment and further verified the reliability of the instruments' response. Then, the average light absorption contribution of BrC aerosol was calculated to be 11.7, 6.3 and 12.1% (with total relative uncertainty of 7.5, 6.9 and 10.0%) at 405nm and 10.0, 4.1 and 5.5% (with total relative uncertainty of 6.5, 8.6 and 15.4%) at 532nm of the three campaigns, respectively. These results indicate that the

  15. Strong enhancement in light absorption by black carbon due to aerosol water uptake

    NASA Astrophysics Data System (ADS)

    Fierce, Laura; Mena, Francisco; Riemer, Nicole; Bond, Tami C.; Bauer, Susanne E.

    2015-04-01

    Black carbon exerts a strong, yet highly uncertain, warming effect on the climate. One source of uncertainty in predicting black carbon's radiative effects is the absorption per black carbon mass. Although models suggest that light absorption is strongly enhanced if black carbon is coated with non-absorbing aerosol material, recent ambient observations find only weak absorption enhancement from aerosol coatings. In this study, we use a particle-resolved aerosol model to evaluate how oversimplified representations of particle composition impact modeled light absorption by black carbon. We show that oversimplifying the representation of particle composition leads to overestimation of modeled absorption enhancement. In order to improve global model representations of BC absorption, we performed a nonparametric regression on particle-reolved model data from a series of simulations. Through this nonparametric analysis we derived a relationship for absorption enhancement as a function of variables that global models already track, the population-averaged composition and the environmental relative humidity. Finally, we show how this nonparametric relationship can be exploited for use in global models to improve predictions of absorption by black carbon. In order to quantify the global-scale impact of water uptake on light absorption by black carbon, we applied the relationship for absorption enhancement to output of the climate model GISS-MATRIX. We find weak absorption enhancement in locations with low relative humidity, but light absorption is strongly enhanced in humid regions. This enhancement in light absorption by particles taking up water strongly impacts black carbon's radiative effects at the global scale, enhancing light absorption by black carbon by 20% relative to dry conditions.

  16. Cloud droplet nucleation and its connection to aerosol properties

    SciTech Connect

    Schwartz, S.E.

    1996-04-01

    Anthropogenic aerosols influence the earth`s radiation balance and climate directly, by scattering shortwave (solar) radiation in cloud-free conditions and indirectly, by increasing concentrations of cloud droplets thereby enhancing cloud shortwave reflectivity. These effects are thought to be significant in the context of changes in the earth radiation budget over the industrial period, exerting a radiative forcing that is of comparable magnitude to that of increased concentrations of greenhouse gases over this period but opposite in sign. However the magnitudes of both the direct and indirect aerosol effects are quite uncertain. Much of the uncertainty of the indirect effect arises from incomplete ability to describe changes in cloud properties arising from anthropogenic aerosols. This paper examines recent studies pertaining to the influence of anthropogenic aerosols on loading and properties of aerosols affecting their cloud nucleating properties and indicative of substantial anthropogenic influence on aerosol and cloud properties over the North Atlantic.

  17. A new approach for retrieving the UV-vis optical properties of ambient aerosols

    NASA Astrophysics Data System (ADS)

    Bluvshtein, Nir; Flores, J. Michel; Segev, Lior; Rudich, Yinon

    2016-08-01

    Atmospheric aerosols play an important part in the Earth's energy budget by scattering and absorbing incoming solar and outgoing terrestrial radiation. To quantify the effective radiative forcing due to aerosol-radiation interactions, researchers must obtain a detailed understanding of the spectrally dependent intensive and extensive optical properties of different aerosol types. Our new approach retrieves the optical coefficients and the single-scattering albedo of the total aerosol population over 300 to 650 nm wavelength, using extinction measurements from a broadband cavity-enhanced spectrometer at 315 to 345 nm and 390 to 420 nm, extinction and absorption measurements at 404 nm from a photoacoustic cell coupled to a cavity ring-down spectrometer, and scattering measurements from a three-wavelength integrating nephelometer. By combining these measurements with aerosol size distribution data, we retrieved the time- and wavelength-dependent effective complex refractive index of the aerosols. Retrieval simulations and laboratory measurements of brown carbon proxies showed low absolute errors and good agreement with expected and reported values. Finally, we implemented this new broadband method to achieve continuous spectral- and time-dependent monitoring of ambient aerosol population, including, for the first time, extinction measurements using cavity-enhanced spectrometry in the 315 to 345 nm UV range, in which significant light absorption may occur.

  18. Model analysis of influences of aerosol mixing state upon its optical properties in East Asia

    NASA Astrophysics Data System (ADS)

    Han, Xiao; Zhang, Meigen; Zhu, Lingyun; Xu, Liren

    2013-07-01

    The air quality model system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) coupled with an aerosol optical/radiative module was applied to investigate the impact of different aerosol mixing states (i.e., externally mixed, half externally and half internally mixed, and internally mixed) on radiative forcing in East Asia. The simulation results show that the aerosol optical depth (AOD) generally increased when the aerosol mixing state changed from externally mixed to internally mixed, while the single scattering albedo (SSA) decreased. Therefore, the scattering and absorption properties of aerosols can be significantly affected by the change of aerosol mixing states. Comparison of simulated and observed SSAs at five AERONET (Aerosol Robotic Network) sites suggests that SSA could be better estimated by considering aerosol particles to be internally mixed. Model analysis indicates that the impact of aerosol mixing state upon aerosol direct radiative forcing (DRF) is complex. Generally, the cooling effect of aerosols over East Asia are enhanced in the northern part of East Asia (Northern China, Korean peninsula, and the surrounding area of Japan) and are reduced in the southern part of East Asia (Sichuan Basin and Southeast China) by internal mixing process, and the variation range can reach ±5 W m-2. The analysis shows that the internal mixing between inorganic salt and dust is likely the main reason that the cooling effect strengthens. Conversely, the internal mixture of anthropogenic aerosols, including sulfate, nitrate, ammonium, black carbon, and organic carbon, could obviously weaken the cooling effect.

  19. AERONET-based microphysical and optical properties of smoke-dominated aerosol near source regions and transported over oceans, and implications for satellite retrievals of aerosol optical depth

    NASA Astrophysics Data System (ADS)

    Sayer, A. M.; Hsu, N. C.; Eck, T. F.; Smirnov, A.; Holben, B. N.

    2013-09-01

    Smoke aerosols from biomass burning are an important component of the global aerosol cycle. Analysis of Aerosol Robotic Network (AERONET) retrievals of size distribution and refractive index reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke transported to coastal/island AERONET sites also mostly lie within the range of variability at near-source sites. Two broad ''families'' of aerosol properties are found, corresponding to sites dominated by boreal forest burning (larger, broader fine mode, with midvisible SSA ∼0.95), and those influenced by grass, shrub, or crop burning with additional forest contributions (smaller, narrower particles with SSA ∼0.88-0.9 in the midvisible). The strongest absorption is seen in southern African savannah at Mongu (Zambia), with average SSA ∼0.85 in the midvisible. These can serve as candidate sets of aerosol microphysical/optical properties for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean are often insufficiently absorbing to represent these biomass burning aerosols. A corollary of this is an underestimate of AOD in smoke outflow regions, which has important consequences for applications of these satellite datasets.

  20. Aeronet-based Microphysical and Optical Properties of Smoke-dominated Aerosol near Source Regions and Transported over Oceans, and Implications for Satellite Retrievals of Aerosol Optical Depth

    NASA Technical Reports Server (NTRS)

    Sayer, A. M.; Hsu, N. C.; Eck, T. F.; Smirnov, A.; Holben, B. N.

    2013-01-01

    Smoke aerosols from biomass burning are an important component of the global aerosol cycle. Analysis of Aerosol Robotic Network (AERONET) retrievals of size distribution and refractive index reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke transported to coastal/island AERONET sites also mostly lie within the range of variability at near-source sites. Two broad families of aerosol properties are found, corresponding to sites dominated by boreal forest burning (larger, broader fine mode, with midvisible SSA 0.95), and those influenced by grass, shrub, or crop burning with additional forest contributions (smaller, narrower particles with SSA 0.88-0.9 in the midvisible). The strongest absorption is seen in southern African savanna at Mongu (Zambia), with average SSA 0.85 in the midvisible. These can serve as candidate sets of aerosol microphysicaloptical properties for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean are often insufficiently absorbing to represent these biomass burning aerosols. A corollary of this is an underestimate of AOD in smoke outflow regions, which has important consequences for applications of these satellite datasets.

  1. Light Absorption of Stratospheric Aerosols: Long-Term Trend and Contribution by Aircraft

    NASA Technical Reports Server (NTRS)

    Pueschel , R. F.; Gore, Waren J. Y. (Technical Monitor)

    1997-01-01

    Measurements of aerosol light-absorption coefficients are useful for studies of radiative transfer and heating rates. Ogren appears to have published the first light- absorption coefficients in the stratosphere in 1981, followed by Clarke in 1983 and Pueschel in 1992. Because most stratospheric soot appears to be due to aircraft operations, application of an aircraft soot aerosol emission index to projected fuel consumption suggests a threefold increase of soot loading and light absorption by 2025. Together, those four data sets indicate an increase in mid-visible light extinction at a rate of 6 % per year. This trend is similar to the increase per year of sulfuric acid aerosol and of commercial fleet size. The proportionality between stepped-up aircraft operations above the tropopause and increases in stratospheric soot and sulfuric acid aerosol implicate aircraft as a source of stratospheric pollution. Because the strongly light-absorbing soot and the predominantly light-scattering sulfuric acid aerosol increase at similar rates, however, the mid-visible stratospheric aerosol single scatter albedo is expected to remain constant and not approach a critical value of 0.98 at which stratospheric cooling could change to warming.

  2. [Development of a photoacoustic spectroscopy system for the measurement of absorption coefficient of atmospheric aerosols].

    PubMed

    Liu, Qiang; Niu, Ming-Sheng; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

    2013-07-01

    In the present paper, the authors focus on the effect of the resonance frequency shift due to the changes in temperature and humidity on the PA signal, present several methods to control the noise derived form gas flow and vibration from the sampling pump. Based on the efforts mentioned above, a detection limit of 1.4 x 10(-8) W x cm(-1) x Hz(-1/2) was achieved for the measurement of atmospheric aerosols absorption coefficient. During the experiments, the PA cell was calibrated with the absorption of standard NO2 gas at 532 nm and the atmospheric aerosols were measured continuously. The measurement results show that the PAS is suitable for the real-time measurement of the absorption coefficient of atmospheric aerosols in their natural suspended state.

  3. Photo-acoustic measurements of gas and aerosol absorption with diode lasers.

    PubMed

    Ponomarev, Yu N

    2004-12-01

    The results of designing multipurpose high-sensitive photo-acoustic (PA) detectors and their application to high-resolution diode laser spectroscopy of molecular gases, gas analysis, and aerosol absorption measurements are summarized in this paper. The hardware and software of the diode laser spectrometer with a Helmholtz resonant PA detector providing an absorption sensitivity limit of better than 10(-7)Wm(-1)Hz(-1/2) are described. A procedure is proposed for an experiment involving the measurements of the rotational structure of hot vibrational bands of molecules. The results of the application of the nonresonant PA cell with temporal resolution of signals to measurements of weak nonresonant absorption of gases and soot aerosols are presented, and the possibility of creating a broad-band PA laser diode aerosol-meter is discussed.

  4. Aerosol Absorption by Black Carbon and Dust: Implications of Climate Change and Air Quality in Asia

    NASA Technical Reports Server (NTRS)

    Chin, Mian

    2010-01-01

    Atmospheric aerosol distributions from 2000 to 2007 are simulated with the global model GOCART to attribute light absorption by aerosol to its composition and sources. We show the seasonal and interannual variations of absorbing aerosols in the atmosphere over Asia, mainly black carbon and dust. and their linkage to the changes of anthropogenic and dust emissions in the region. We compare our results with observations from satellite and ground-based networks, and estimate the importance of black carbon and dust on regional climate forcing and air quality.

  5. Uncertainties in Carbonaceous Aerosol Emissions, Scavenging Parameterizations, and Optical Properties

    NASA Astrophysics Data System (ADS)

    Koch, D.; Bond, T.; Kinne, S.; Klimont, Z.; Sun, H.; van Aardenne, J.; van der Werf, G.

    2006-12-01

    Estimates of human influence on climate are especially hindered by poor constraint on the amount of anthropogenic carbonaceous aerosol absorption in the atmosphere. Coordination of observation and model analyses attempt to constrain particle absorption amount, however these are limited by uncertainties in aerosol emission estimates, model scavenging parameterization, aerosol size assumption, contributions from organic aerosol absorption, air concentration observational techniques and by sparsity of data coverage. We perform multiple simulations using GISS modelE and six present-day emission estimates for black carbon (BC) and organic carbon (OC) (Bond et al 2004 middle and upper estimates, IIASA, EDGAR, GFED v1 and v2); for one of these emissions we apply 4 different BC/OC scavenging parameterizations. The resulting concentrations will be compared with a new compilation of observed BC/OC concentrations. We then use these model concentrations, together with effective radius assumptions and estimates of OC absorption to calculate a range of carbonaceous aerosol absorption. We constrain the wavelength-dependent model τ- absorption with AERONET sun-photometer observations. We will discuss regions, seasons and emission sectors with greatest uncertainty, including those where observational constraint is lacking. We calculate the range of model radiative forcing from our simulations and discuss the degree to which it is constrained by observations.

  6. Optical and Structural Properties of Aerosols Emitted from Open Biomass Burning (Invited)

    NASA Astrophysics Data System (ADS)

    Moosmuller, H.; Chakrabarty, R. K.; Lewis, K.; Gyawali, M.; Mazzoleni, C.; Dubey, M. K.; Kreidenweis, S. M.; Arnott, W. P.

    2010-12-01

    Open biomass burning including wildland fires and agricultural burning emits substantial quantities of carbonaceous aerosols into the atmosphere. Fuel, soil, and atmospheric conditions largely determine the combustion phase. High temperature flaming combustion emits black aerosols, generally consisting of fractal-like chain aggregates that have a high black carbon content and therefore strongly absorb visible light. Low temperature, smoldering combustion, on the other hand, emits fairly white aerosols, often consisting of near-spherical particles that have high organic carbon content. While this organic carbon is traditionally considered to cause negligent absorption of visible light, more recent studies have shown that organic carbon from biomass burning often contains brown carbon. Brown carbon is a component of organic carbon, optically defined by its increasing light absorption toward shorter wavelengths. The physical characteristics of biomass combustion aerosol particles are determined by a combination of their morphology, monomer size, and shape, all of which can be determined from electron microscopy and image analysis. Here, we review optical and structural properties of aerosols emitted from open biomass burning with a focus on relevance for radiative forcing and climate change and satellite remote sensing. This review is followed by a discussion of measurements and modeling of brown carbon optical properties, of associated metrics such as the Ångström absorption coefficient, and of future research needs.

  7. Aerosol and CCN properties at Princess Elisabeth station, East Antarctica: seasonality, new particle formation events and properties around precipitation events

    NASA Astrophysics Data System (ADS)

    Mangold, Alexander; Laffineur, Quentin; De Backer, Hugo; Herenz, Paul; Wex, Heike; Gossart, Alexandra; Souverijns, Niels; Gorodetskaya, Irina; Van Lipzig, Nicole

    2016-04-01

    Since 2010, several complementary ground-based instruments for measuring the aerosol composition of the Antarctic atmosphere have been operated at the Belgian Antarctic research station Princess Elisabeth, in Dronning Maud Land, East Antarctica (71.95° S, 23.35° E, 1390 m asl.). In addition, three ground-based remote sensing instruments for cloud and precipitation observations have been installed for continuous operation, including a ceilometer (cloud base height, type, vertical extent), a 24 Ghz micro-rain radar (vertical profiles of radar effective reflectivity and Doppler velocity), and a pyrometer (cloud base temperature). The station is inhabited from November to end of February and operates under remote control during the other months. In this contribution, the general aerosol and cloud condensation nuclei (CCN) properties will be described with a special focus on new particle formation events and around precipitation events. New particle formation events are important for the atmospheric aerosol budget and they also show that aerosols are not only transported to Antarctica but are also produced there, also inland. Aerosols are essential for cloud formation and therefore also for precipitation, which is the only source for mass gain of the Antarctic ice sheet. Measured aerosol properties comprise size distribution, total number, total mass concentration, mass concentration of light-absorbing aerosol and absorption coefficient and total scattering coefficient. In addition, a CCN counter has been operated during austral summers 2013/14, 2014/15 and 2015/16. The baseline total number concentration N-total was around some hundreds of particles/cm3. During new particle formation events N-total increased to some thousands of particles/cm3. Simultaneous measurements of N-total, size distribution and CCN number revealed that mostly the number of particles smaller than 100 nm increased and that the concentration of cloud condensation nuclei increased only very

  8. The surface aerosol optical properties in the urban area of Nanjing, west Yangtze River Delta, China

    NASA Astrophysics Data System (ADS)

    Zhuang, Bingliang; Wang, Tijian; Liu, Jane; Li, Shu; Xie, Min; Han, Yong; Chen, Pulong; Hu, Qiduo; Yang, Xiu-qun; Fu, Congbin; Zhu, Jialei

    2017-01-01

    Observational studies of aerosol optical properties are useful for reducing uncertainties in estimations of aerosol radiative forcing and forecasting visibility. In this study, the observed near-surface aerosol optical properties in urban Nanjing are analysed from March 2014 to February 2016. Results show that near-surface urban aerosols in Nanjing are mainly from local emissions and the surrounding regions. They have lower loadings but are more scattering than aerosols in most cities in China. The annual mean aerosol extinction coefficient (EC), single-scattering albedo (SSA) and asymmetry parameter (ASP) at 550 nm are 381.96 Mm-1, 0.9 and 0.57, respectively. The aerosol absorption coefficient (AAC) is about 1 order of magnitude smaller than its scattering coefficient (SC). However, the absorbing aerosol has a larger Ångström exponent (AAE) value, 1.58 at 470/660 nm, about 0.2 larger than the scattering aerosols (SAE). All the aerosol optical properties follow a near-unimodal pattern, and their values are mostly concentrated around their averages, accounting for more than 60 % of the total samplings. Additionally, they have substantial seasonality and diurnal variations. High levels of SC and AAC all appear in winter due to higher aerosol and trace gas emissions. AAE (ASP) is the smallest (largest) in summer, possibly because of high relative humidity (RH) which also causes considerably larger SC and smaller SAE, although intensive gas-to-particle transformation could produce a large number of finer scattering aerosols in this season. Seasonality of EC is different from the columnar aerosol optical depth. Larger AACs appear during the rush hours of the day while SC and back-scattering coefficient (Bsp) only peak in the early morning. Aerosols are fresher in the daytime than at night-time, leading to their larger Ångström exponent and smaller ASP. Different temporal variations between AAC and SC cause the aerosols to be more absorbing (smaller SSA) in autumn

  9. Elevated aerosol layers modify the O2–O2 absorption measured by ground-based MAX-DOAS

    SciTech Connect

    Ortega, Ivan; Berg, Larry K.; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Volkamer, Rainer

    2016-06-01

    The oxygen collisional complex (O2-O2, or O4) is a greenhouse gas, and a calibration trace gas used to infer aerosol and cloud properties by Differential Optical Absorption Spectroscopy (DOAS). Recent reports suggest the need for an O4 correction factor (CFO4) when comparing simulated and measured O4 differential slant column densities (dSCD) by passive DOAS. We investigate the sensitivity of O4 dSCD simulations at ultraviolet (360 nm) and visible (477 nm) wavelengths towards separately measured aerosol extinction profiles. Measurements were conducted by the University of Colorado 2D-MAX-DOAS instrument and NASA’s multispectral High Spectral Resolution Lidar (HSRL-2) during the Two Column Aerosol Project (TCAP) at Cape Cod, MA in July 2012. During two case study days with (1) high aerosol load (17 July, AOD ~ 0.35 at 477 nm), and (2) near molecular scattering conditions (22 July, AOD < 0.10 at 477 nm) the measured and calculated O4 dSCDs agreed within 6.4±0.4% (360 nm) and 4.7±0.6% (477 nm) if the HSRL-2 profiles were used as input to the calculations. However, if in the calculations the aerosol is confined to the surface layer (while keeping AOD constant) we find 0.53aerosol layers, unless accounted for, can cause negative bias in the simulated O4 dSCDs that can explain CFO4. The air density and aerosol profile aloft needs to be taken into account when interpreting the O4 from ground-based MAX-DOAS. Opportunities to identify and better characterize these layers are also discussed.

  10. A photophonic instrument concept to measure atmospheric aerosol absorption. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Engle, C. D.

    1982-01-01

    A laboratory model of an instrument to measure the absorption of atmospheric aerosols was designed, built, and tested. The design was based on the photophonic phenomenon discovered by Bell and an acoustic resonator developed by Helmholtz. Experiments were done to show ways the signal amplitude could be improved and the noise reduced and to confirm the instrument was sensitive enough to be practical. The research was undertaken to develop concepts which show promise of being improvements on the instruments that are presently used to measure the absorption of the Sun's radiation by the Earth's atmospheric aerosols.

  11. Detection of a gas flaring signature in the AERONET optical properties of aerosols at a tropical station in West Africa

    NASA Astrophysics Data System (ADS)

    Fawole, Olusegun G.; Cai, Xiaoming; Levine, James G.; Pinker, Rachel T.; MacKenzie, A. R.

    2016-12-01

    The West African region, with its peculiar climate and atmospheric dynamics, is a prominent source of aerosols. Reliable and long-term in situ measurements of aerosol properties are not readily available across the region. In this study, Version 2 Level 1.5 Aerosol Robotic Network (AERONET) data were used to study the absorption and size distribution properties of aerosols from dominant sources identified by trajectory analysis. The trajectory analysis was used to define four sources of aerosols over a 10 year period. Sorting the AERONET aerosol retrievals by these putative sources, the hypothesis that there exists an optically distinct gas flaring signal was tested. Dominance of each source cluster varies with season: desert-dust (DD) and biomass burning (BB) aerosols are dominant in months prior to the West African Monsoon (WAM); urban (UB) and gas flaring (GF) aerosol are dominant during the WAM months. BB aerosol, with single scattering albedo (SSA) at 675 nm value of 0.86 ± 0.03 and GF aerosol with SSA (675 nm) value of 0.9 ± 0.07, is the most absorbing of the aerosol categories. The range of Absorption Angstr&öm Exponent (AAE) for DD, BB, UB and GF classes are 1.99 ± 0.35, 1.45 ± 0.26, 1.21 ± 0.38 and 0.98 ± 0.25, respectively, indicating different aerosol composition for each source. The AAE (440-870 nm) and Angstr&öm Exponent (AE) (440-870 nm) relationships further show the spread and overlap of the variation of these optical and microphysical properties, presumably due in part to similarity in the sources of aerosols and in part, due to mixing of air parcels from different sources en route to the measurement site.

  12. Optical properties of aerosol emissions from biomass burning in the tropics, BASE-A

    NASA Technical Reports Server (NTRS)

    Holben, Brent N.; Kaufman, Yoram J.; Setzer, Alberto W.; Tanre, Didre D.; Ward, Darold E.

    1991-01-01

    Ground-based and airborne measurements of biomass-burning smoke particle optical properties, obtained with a view to aerosol-absorption properties, are presented as a function of time and atmospheric height. The wavelength dependence of the optical thickness can be explained by a log-normal size distribution, with particles' effective radius varying between 0.1 and 0.2 microns. The strong correlation noted between aerosol particle profile and CO profile indicates that smoke particulates constitute a good tracer for emission trace gases from tropical biomass burning.

  13. Characterization of aerosol properties from polarimetric satellite observations using GRASP algorithm

    NASA Astrophysics Data System (ADS)

    Dubovik, Oleg; Litvinov, Pavel; Lapyonok, Tatyana; Ducos, Fabrice; Huang, Xin; Lopatin, Anton; Fuertes, David; Derimian, Yevgeny

    2016-04-01

    GRASP (Generalized Retrieval of Aerosol and Surface Properties) is recently developed (Dubovik et al. 2011, 2014) sophisticated algorithm of new generation. The algorithm retrieves aerosol and surface properties simultaneously. It realizes statistically optimized fitting using multi-pixel concept when the retrieval is implemented simultaneously for a large group of satellite pixels. This allows for using additional a priori information about limited variability of aerosol of surface properties in time and/or space. GPASP searches in continuous space of solutions and doesn't utilize look-up-tables. GRASP doesn't use any location specific information about aerosol or surface type in the each observed pixel, and the results are essentially driven by observations. However GRASP retrieval takes longer computational time compare to most conventional algorithms. This main practical challenge of employing GRASP has been addressed during last two years and GRASP algorithm has been significantly optimized and adapted to operational needs. As a result of this optimization and GRASP has been accelerated to the level acceptable for processing large volumes of satellite observations. Recently GRASP has been applied to multi-years archives of PARASO/POLDER. The analysis of the results shows that GRASP retrievals provide rather robust and comprehensive aerosol characterization including such properties as absorption and aerosol type even for observations over bright surfaces and for monitoring very high aerosol loading events (with AOD up to 3 or 4). In addition, the attempts to estimate such aerosol characteristics as aerosol height, air quality, radiative forcing, etc. have been made. The results and illustrations will be presented.

  14. Long term measurements of aerosol optical properties at a primary forest site in Amazonia

    NASA Astrophysics Data System (ADS)

    Rizzo, L. V.; Artaxo, P.; Müller, T.; Wiedensohler, A.; Paixão, M.; Cirino, G. G.; Arana, A.; Swietlicki, E.; Roldin, P.; Fors, E. O.; Wiedemann, K. T.; Leal, L. S. M.; Kulmala, M.

    2013-03-01

    A long term experiment was conducted in a primary forest area in Amazonia, with continuous in-situ measurements of aerosol optical properties between February 2008 and April 2011, comprising, to our knowledge, the longest database ever in the Amazon Basin. Two major classes of aerosol particles, with significantly different optical properties were identified: coarse mode predominant biogenic aerosols in the wet season (January-June), naturally released by the forest metabolism, and fine mode dominated biomass burning aerosols in the dry season (July-December), transported from regional fires. Dry particle median scattering coefficients at the wavelength of 550 nm increased from 6.3 Mm-1 to 22 Mm-1, whereas absorption at 637 nm increased from 0.5 Mm-1 to 2.8 Mm-1 from wet to dry season. Most of the scattering in the dry season was attributed to the predominance of fine mode (PM2) particles (40-80% of PM10 mass), while the enhanced absorption coefficients are attributed to the presence of light absorbing aerosols from biomass burning. As both scattering and absorption increased in the dry season, the single scattering albedo (SSA) did not show a significant seasonal variability, in average 0.86 ± 0.08 at 637 nm for dry aerosols. Measured particle optical properties were used to estimate the aerosol forcing efficiency at the top of the atmosphere. Results indicate that in this primary forest site the radiative balance was dominated by the cloud cover, particularly in the wet season. Due to the high cloud fractions, the aerosol forcing efficiency absolute values were below -3.5 W m-2 in 70% of the wet season days and in 46% of the dry season days. Besides the seasonal variation, the influence of out-of-Basin aerosol sources was observed occasionally. Periods of influence of the Manaus urban plume were detected, characterized by a consistent increase on particle scattering (factor 2.5) and absorption coefficients (factor 5). Episodes of biomass burning and mineral dust

  15. Long term measurements of aerosol optical properties at a pristine forest site in Amazonia

    NASA Astrophysics Data System (ADS)

    Rizzo, L. V.; Artaxo, P.; Müller, T.; Wiedensohler, A.; Paixão, M.; Cirino, G. G.; Arana, A.; Swietlicki, E.; Roldin, P.; Fors, E. O.; Wiedemann, K. T.; Leal, L. S. M.; Kulmala, M.

    2012-09-01

    A long term experiment was conducted in a pristine area in the Amazon forest, with continuous in situ measurements of aerosol optical properties between February 2008 and April 2011, comprising, to our knowledge, the longest database ever in Amazonia. Two types of aerosol particles, with significantly different optical properties were identified: coarse mode predominant biogenic aerosols in the wet season (January-June), naturally released by the forest metabolism, and fine mode dominated biomass burning aerosols in the dry season (July-December), transported from regional fires. Dry particle median scattering coefficients at the wavelength of 550 nm increased from 6.3 Mm-1 to 22 Mm-1, whereas absorption at 637 nm increased from 0.5 Mm-1 to 2.8 Mm-1 from wet to dry season. Most of the scattering in the dry season was attributed to the predominance of fine mode particles (40-80% of PM10 mass), while the enhanced absorption coefficients are attributed to the presence of light absorbing aerosols from biomass burning. As both scattering and absorption increased in the dry season, the single scattering albedo (SSA) did not show a significant seasonal variability, in average 0.86 ± 0.08 at 637 nm for dry particles. Measured particle optical properties were used to estimate the aerosol forcing efficiency at the top of the atmosphere. Results indicate that in this pristine forest site the radiative balance was dominated by the cloud cover, or, in other words, the aerosol indirect effect predominated over the direct effect, particularly in the wet season. Due to the high cloud fractions, the aerosol forcing efficiency was below -3.5 W m-2 in 70% of the wet season days and in 46% of the dry season days. These values are lower than the ones reported in the literature, which are based on remote sensing data. Besides the seasonal variation, the influence of external aerosol sources was observed occasionally. Periods of influence of the Manaus urban plume were detected

  16. Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds

    SciTech Connect

    Richard A. Ferrare; David D. Turner

    2011-09-01

    Project goals: (1) Use the routine surface and airborne measurements at the ARM SGP site, and the routine surface measurements at the NSA site, to continue our evaluations of model aerosol simulations; (2) Determine the degree to which the Raman lidar measurements of water vapor and aerosol scattering and extinction can be used to remotely characterize the aerosol humidification factor; (3) Use the high temporal resolution CARL data to examine how aerosol properties vary near clouds; and (4) Use the high temporal resolution CARL and Atmospheric Emitted Radiance Interferometer (AERI) data to quantify entrainment in optically thin continental cumulus clouds.

  17. Climatology of Aerosol Optical Properties in Southern Africa

    NASA Technical Reports Server (NTRS)

    Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

    2011-01-01

    A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with

  18. Airborne in situ characterization of dry urban aerosol optical properties around complex topography

    NASA Astrophysics Data System (ADS)

    Targino, Admir Créso; Noone, Kevin J.

    2006-02-01

    In situ data from the 1997 Southern California Ozone Study—NARSTO were used to describe the aerosol optical properties in an urban area whose aerosol distribution is modified as the aerosols are advected over the surrounding topography. The data consist of measurements made with a nephelometer and absorption photometer onboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Pelican aircraft. The cases investigated in this study include vertical profiles flown over coastal sites as well as sites located along some important mountain ranges in southern California. The vertical distribution of the aerosol in the Los Angeles Basin showed a complex configuration, directly related with the local meteorological circulations and the surrounding topography. High spatial and temporal variability in air pollutant concentrations within a relatively small area was found, as indicated by the aerosol scattering and absorption coefficient data. The results suggest that in areas with such complex terrain, a high spatial resolution is required in order to adequately describe the aerosol optical quantities. Principal components analysis (PCA) has been applied to aerosol chemical samples in order to identify the major aerosol types in the Los Angeles Basin. The technique yielded four components that accounted for 78% of the variance in the data set. These were indicative of marine aerosols, urban aerosols, trace elements and secondary aerosol components of traffic emissions and agricultural activities. A Monte Carlo radiation transfer model has been employed to simulate the effects that different aerosol vertical profiles have on the attenuation of solar energy. The cases examined were selected using the results of the PCA and in situ data were used to describe the atmospheric optical properties in the model. These investigations comprise a number of sensitivity tests to evaluate the effects on the results of the location of the aerosol layers as well as

  19. Measurements of Aerosol Vertical Profiles and Optical Properties during INDOEX 1999 Using Micro-Pulse Lidars

    NASA Technical Reports Server (NTRS)

    Welton, Ellsworth J.; Voss, Kenneth J.; Quinn, Patricia K.; Flatau, Piotr J.; Markowicz, Krzysztof; Campbell, James R.; Spinhirne, James D.; Gordon, Howard R.; Johnson, James E.; Starr, David OC. (Technical Monitor)

    2001-01-01

    Micro-pulse lidar systems (MPL) were used to measure aerosol properties during the Indian Ocean Experiment (INDOEX) 1999 field phase. Measurements were made from two platforms: the NOAA ship RN Ronald H. Brown, and the Kaashidhoo Climate Observatory (KCO) in the Maldives. Sunphotometers were used to provide aerosol optical depths (AOD) needed to calibrate the MPL. This study focuses on the height distribution and optical properties (at 523 nm) of aerosols observed during the campaign. The height of the highest aerosols (top height) was calculated and found to be below 4 km for most of the cruise. The marine boundary layer (MBL) top was calculated and found to be less than 1 km. MPL results were combined with air mass trajectories, radiosonde profiles of temperature and humidity, and aerosol concentration and optical measurements. Humidity varied from approximately 80% near the surface to 50% near the top height during the entire cruise. The average value and standard deviation of aerosol optical parameters were determined for characteristic air mass regimes. Marine aerosols in the absence of any continental influence were found to have an AOD of 0.05 +/- 0.03, an extinction-to-backscatter ratio (S-ratio) of 33 +/- 6 sr, and peak extinction values around 0.05/km (near the MBL top). The marine results are shown to be in agreement with previously measured and expected values. Polluted marine areas over the Indian Ocean, influenced by continental aerosols, had AOD values in excess of 0.2, S-ratios well above 40 sr, and peak extinction values approximately 0.20/km (near the MBL top). The polluted marine results are shown to be similar to previously published values for continental aerosols. Comparisons between MPL derived extinction near the ship (75 m) and extinction calculated at ship-level using scattering measured by a nephelometer and absorption using a PSAP were conducted. The comparisons indicated that the MPL algorithm (using a constant S-ratio throughout the

  20. Experimental validation of light scattering and absorption theories of fractal-like carbonaceous aerosol agglomerates

    NASA Astrophysics Data System (ADS)

    Chakrabarty, R.; Moosmuller, H.; Arnott, W. P.; Garro, M.; Slowik, J.; Cross, E.; Han, J.; Davidovits, P.; Onasch, T.; Worsnop, D.

    2007-12-01

    The optical coefficients of size-selected carbonaceous aerosol agglomerates measured at a wavelength of 870 nm are compared with those predicted by three theories, namely Rayleigh-Debye-Gans (RDG) approximation, volume-equivalent Mie theory, and integral equation formulation for scattering (IEFS). Carbonaceous agglomerates, produced via flame synthesis, were size-selected using two differential mobility analyzers (DMAs) in series, and their scattering and absorption coefficients were measured with nephelometry and photoacoustic spectroscopy. Scanning electron microscopy, along with image processing techniques, were used for the parameterization of the structural properties of the fractal-like agglomerates. The agglomerate structural parameters were used to evaluate the predictions of the optical coefficients based on the three light scattering and absorption theories. The results indicate that the RDG approximation agrees within 10% of the experimental results and the exact electromagnetic calculations of the IEFS theory. The experimental scattering coefficient is over predicted by the volume-equivalent Mie theory by a factor of ~3.2. Also, the RDG approximation-predicted optical coefficients showed pronounced sensitivity to changes in monomer mean diameter, the count median diameter of the agglomerates, and the geometric standard deviation of the agglomerate number size distribution.

  1. Aerosol optical properties in the ABL over arctic sea ice from airborne aerosol lidar measurements

    NASA Astrophysics Data System (ADS)

    Schmidt, Lukas; Neuber, Roland; Ritter, Christoph; Maturilli, Marion; Dethloff, Klaus; Herber, Andreas

    2014-05-01

    Between 2009 and 2013 aerosols, sea ice properties and meteorological variables were measured during several airborne campaigns covering a wide range of the western Arctic Ocean. The campaigns were carried out with the aircraft Polar 5 of the German Alfred-Wegener-Institute (AWI) during spring and summer periods. Optical properties of accumulation mode aerosol and clouds were measured with the nadir looking AMALi aerosol lidar covering the atmospheric boundary layer and the free troposphere up to 3000m, while dropsondes provided coincident vertical profiles of meteorological quantities. Based on these data we discuss the vertical distribution of aerosol backscatter in and above the atmospheric boundary layer and its dependence on relative humidity, dynamics and underlying sea ice properties. We analyze vertical profiles of lidar and coincident dropsonde measurements from various locations in the European and Canadian Arctic from spring and summer campaigns. Sea ice cover is derived from modis satellite and aircraft onboard camera images. The aerosol load in the arctic atmospheric boundary layer shows a high variability. Various meteorological parameters and in particular boundary layer properties are discussed with their respective influence on aerosol features. To investigate the effect of the frequency and size of open water patches on aerosol properties, we relate the profiles to the sea ice properties influencing the atmosphere in the upwind region.

  2. Optical and chemical properties of aerosols transported to Mount Bachelor during spring 2010

    NASA Astrophysics Data System (ADS)

    Fischer, E. V.; Perry, K. D.; Jaffe, D. A.

    2011-09-01

    We report on springtime 2010 observations of aerosol optical properties and size-resolved elemental composition from Mount Bachelor Observatory (MBO; 2763 meters above sea level). Observations included multiwavelength aerosol scattering and absorption, made with a nephelometer and a particle soot absorption photometer, and size-resolved composition, made using a rotating DRUM impactor with substrates analyzed by synchrotron X-ray fluorescence. Our main tool for investigating variability in composition was empirical orthogonal function (EOF) analysis. In April, dust and sulfate explained 96% of the variance in the observed fine composition and accounted for the majority of the fine mode scattering. Three coincident Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation overpasses also identified aerosol layers classified as dust or polluted dust over MBO. Later in the spring, we deduce that organics and nitrate comprised more than 50% of the submicrometer aerosol mass. We used the EOF analysis to identify systematic relationships between composition and optical properties. We observed dust accompanied by anthropogenic pollutants including sulfate. When present, dust aerosol controlled ˜30% of the variability in the wavelength dependence of fine mode scattering. Many of the samples containing sulfate had absorption Ångstrom exponents near 1, suggesting black carbon was also present. Most of the sulfate was in the fine mode, but sulfate was also observed on coarse aerosols, and we inferred that much of the coarse sulfur was coated on the dust or had formed CaSO4 during transport. The relationships between Fe, Ca, Al, and Si observed at MBO were consistent with previous observations of Asian dust transported to North America.

  3. Determination of Marine Aerosol Properties Using a Bistatic Nephelometer

    DTIC Science & Technology

    2016-06-07

    light scattered by aerosols. The information derived from these measurements will enable accurate prediction of the aerosol optical properties and...consequently their effect on light propagation in the MABL. OBJECTIVES The objective of this work is to develop and deploy a new light scattering...instrument to remotely characterize atmospheric aerosols. The bi-static nephelometer (an instrument with separately pointed light source and detector that

  4. Martian aerosols: Near-infrared spectral properties and effects on the observation of the surface

    NASA Technical Reports Server (NTRS)

    Erard, Stephane; Mustard, John; Murchie, Scott; Bibring, Jean-Pierre; Cerroni, Priscilla; Caradini, Angioletta

    1994-01-01

    Imaging sprectroscopic measurements (ISM) of Mars acquired by the ISM instrument on Phobos-2 are used to investigate the NIR spectral properties of aerosols and the effects of atmospheric scattering on inferred mineralogy of the surface. Estimates of aerosols spectra between 0.77 and 2.6 micrometers are derived above Tharsis and Ophir Planum. The spectral continua are consistent with the particle size distribution derived using data from the solar occultation experiment on-board the spacecraft (effective radius approximately = 1.2 micrometers, with an effective variance approximately = 0.2). The aerosols spectra contain water-ice absorption features and possibly absorptions due to clay and/or sulfates. The largest effect of the aerosols on surface spectra is in dark regions, where the continuum spectral slope becomes more negative and the 1-micrometers absorption due to Fe in pyroxene is shifted toward longer wavelengths. The effects of aerosols on spectra of bright regions are insufficiently large to change mineralogic interpretations based on ISM data, i.e., that bright regions in Tharsis are dominated spectrally by hematite, but that additional ferric minerals are probably present in other areas including Arabia.

  5. Aerosol Properties over the Indo-Gangetic Plain: A Mesoscale Perspective from the TIGERZ Experiment

    NASA Technical Reports Server (NTRS)

    Giles, David M.; Holben, Brent N.; Tripathi, Sachchida; Eck, Thomas F.; Newcomb, W. Wayne; Slutsker, Ilya; Dickerson, Russell R.; Thompson, Anne M.; Mattoo, Shana; Wang, Sheng-Hsiang; Singh, Remesh P.; Sinyuk, Aliaksandr; Schafer, Joel S.

    2011-01-01

    High aerosol loading over the northern Indian subcontinent can result in poor air quality leading to human health consequences and climate perturbations. The international 2008 TIGERZ experiment intensive operational period (IOP) was conducted in the Indo \\Gangetic Plain (IGP) around the industrial city of Kanpur (26.51degN, 80.23deg E), India, during the premonsoon (April-June). Aerosol Robotic Network (AERONET) Sun photometers performed frequent measurements of aerosol properties at temporary sites distributed within an area covering 50 sq km around Kanpur to characterize pollution and dust in a region where complex aerosol mixtures and semi \\bright surface effects complicate satellite retrieval algorithms. TIGERZ IOP Sun photometers quantified aerosol optical depth (AOD) increases up to 0.10 within and downwind of the city, with urban emissions accounting for 10 C20% of the IGP aerosol loading on deployment days. TIGERZ IOP area \\averaged volume size distribution and single scattering albedo retrievals indicated spatially homogeneous, uniformly sized, spectrally absorbing pollution and dust particles. Aerosol absorption and size relationships were used to categorize black carbon and dust as dominant absorbers and to identify a third category in which both black carbon and dust dominate absorption.Moderate Resolution Imaging Spectroradiometer (MODIS) AOD retrievals with the lowest quality assurance (QA > or = 0) flags were biased high with respect to TIGERZ IOP area \\averaged measurements. MODIS AOD retrievals with QA 0 had moderate correlation (R(sup 2) = 0.52-69) with the Kanpur AERONET site, whereas retrievals with QA > 0 were limited in number. Mesoscale \\distributed Sun photometers quantified temporal and spatial variability of aerosol properties, and these results were used to validate satellite retrievals.

  6. Laboratory Measurements of the Effect of Sulfuric and Organic Acid Coatings on the Optical Properties of Carbon Soot Aerosols

    NASA Astrophysics Data System (ADS)

    Xue, H.; Khalizov, A.; Zhang, R.

    2008-12-01

    Aerosol particles perturb the Earth-atmosphere radiative balance through scattering and absorption of the solar energy. Soot or black carbon, produced during combustion of fossil fuels and biofuels, is the major component responsible for light absorption by aerosol particles. The variation in the reported mass-specific absorption cross-sections (MAC) of fresh soot and increased light absorption by aged soot aerosols internally mixed with non-absorbing materials are the major factors leading to large uncertainties in the evaluation of the aerosol optical effects. We have investigated the optical properties of submicron carbon soot aerosols during simulated atmospheric processing with sulfuric acid and dicarboxylic organic acids. Internally mixed soot particles with known size, morphology, and the mixing state were produced by exposing the size-classified, flame-generated soot to sulfuric acid and organic acid vapor. Light extinction and scattering by fresh and internally mixed soot were measured at 532 nm wavelength using a cavity ring-down spectrometer and an integrating nephelometer, respectively; light absorption was derived as the difference between extinction and scattering. Mass-specific absorption cross-sections for fresh and internally mixed soot aggregates were calculated using the measured effective densities of soot cores. The optical properties of fresh soot were independent of the relative humidity (RH). Internally mixed soot exhibited significant enhancement in light absorption and scattering, increasing with the mass fraction of the coating material and RH. Sulfuric acid was found to cause greater enhancement in soot optical properties than organic acids. The higher absorption and scattering resulted in the increased single scattering albedo of coated soot aerosol. The measurements indicate that the irreversible restructuring of soot aggregates to more compact globules is a major contributor to the enhanced optical properties of internally mixed soot.

  7. Reduction in biomass burning aerosol light absorption upon humidification: Roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer

    SciTech Connect

    lewis, Kristen A.; Arnott, W. P.; Moosmuller, H.; Chakrabarti, Raj; Carrico, Christian M.; Kreidenweis, Sonia M.; Day, Derek E.; Malm, William C.; Laskin, Alexander; Jimenez, Jose L.; Ulbrich, Ingrid M.; Huffman, John A.; Onasch, Timothy B.; Trimborn, Achim; Liu, Li; Mishchenko, M.

    2009-11-27

    Smoke particle emissions from the combustion of biomass fuels typical for the western and southeastern United States were studied and compared under high humidity and ambient conditions in the laboratory. The fuels used are Montana ponderosa pine (Pinus ponderosa), southern California chamise (Adenostoma fasciculatum), and Florida saw palmetto (Serenoa repens). Information on the non-refractory chemical composition of biomass burning aerosol from each fuel was obtained with an aerosol mass spectrometer and through estimation of the black carbon concentration from light absorption measurements at 870 nm. Changes in the optical and physical particle properties under high humidity conditions were observed for hygroscopic smoke particles containing substantial inorganic mass fractions that were emitted from combustion of chamise and palmetto fuels. Light scattering cross sections increased under high humidity for these particles, consistent with the hygroscopic growth measured for 100 nm particles in HTDMA measurements. Photoacoustic measurements of aerosol light absorption coefficients reveal a 20% reduction with increasing relative humidity, contrary to the expectation of light absorption enhancement by the liquid coating taken up by hygroscopic particles. This reduction is hypothesized to arise from two mechanisms: 1. Shielding of inner monomers after particle consolidation or collapse with water uptake; 2. The contribution of mass transfer through evaporation and condensation at high relative humidity to the usual heat transfer pathway for energy release by laser heated particles in the photoacoustic measurement of aerosol light absorption. The mass transfer contribution is used to evaluate the fraction of aerosol surface covered with liquid water solution as a function of RH.

  8. Aerosol activation properties and CCN closure during TCAP

    NASA Astrophysics Data System (ADS)

    Mei, F.; Tomlinson, J. M.; Shilling, J. E.; Wilson, J. M.; Zelenyuk, A.; Chand, D.; Comstock, J. M.; Hubbe, J.; Berg, L. K.; Schmid, B.

    2013-12-01

    The indirect effects of atmospheric aerosols currently remain the most uncertain components in forcing of climate change over the industrial period (IPCC, 2007). This large uncertainty is partially due to our incomplete understanding of the ability of particles to form cloud droplets under atmospherically relevant supersaturation. In addition, there is a large uncertainty in the aerosol optical depth (AOD) simulated by climate models near the North American coast and a wide variety in the types of clouds are observed over this region. The goal of the US Department of Energy Two Column Aerosol Project (TCAP) is to understand the processes responsible for producing and maintaining aerosol distributions and associated radiative and cloud forcing off the coast of North America. During the TCAP study, aerosol total number concentration, cloud condensation nuclei (CCN) spectra and aerosol chemical composition were in-situ measured from the DOE Gulfstream 1 (G-1) research aircraft during two Intensive Operations Periods (IOPs), one conducted in July 2012 and the other in February 2013. An overall aerosol size distribution was achieved by merging the observations from several instruments, including Ultra High Sensitivity Aerosol Spectrometer - Airborne (UHSAS-A, DMT), Passive Cavity Aerosol Spectrometer Probe (PCASP-200, DMT), and Cloud Aerosol Spectrometer (CAS, DMT). Aerosol chemical composition was characterized using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS, Aerodyne Inc.) and single particle mass spectrometer, mini-SPLAT. Based on the aerosol size distribution, CCN number concentration (characterized by a DMT dual column CCN counter with a range from 0.1% to 0.4%), and chemical composition, a CCN closure was obtained. The sensitivity of CCN closure to organic hygroscopicity was investigated. The differences in aerosol/CCN properties between two columns, and between two phases, will be discussed.

  9. An investigation of aerosol optical properties: Atmospheric implications and influences

    NASA Astrophysics Data System (ADS)

    Penaloza-Murillo, Marcos A.

    An experimental, observational, and theoretical investigation of aerosol optical properties has been made in this work to study their implications and influences on the atmosphere. In the laboratory the scientific and instrumental methodology consisted of three parts, namely, aerosol generation, optical and mass concentration measurements, and computational calculations. In particular the optical properties of ammonium sulfate and caffeine aerosol were derived from measurements made with a transmissometer cell-reciprocal- integrating nephelometer (TCRIN), equipped with a laser beam at 632.8 nm, and by applying a Mie theory computer code The aerosol generators, optical equipment and calibration procedures were reviewed. The aerosol shape and size distribution were studied by means of scanning electron microscopy and the Gumprecht- Sliepcevich/Lipofsky-Green extinction-sedimentation method. In particular the spherical and cylindrical shape were considered. During this investigation, an alternative method for obtaining the optical properties of monodisperse spherical non-absorbing aerosol using a cell-transmissometer, which is based on a linearisation of the Lambert-Beer law, was found. In addition, adapting the TCRIN to electrooptical aerosol studies, the optical properties of a circular-cylindrical aerosol of caffeine were undertaken under the condition of random orientation in relation with the laser beam, and perpendicular orientation to it. A theoretical study was conducted to assess the sensitivity of aerosol to a change of shape under different polarisation modes. The aerosol optical properties, obtained previously in the laboratory, were then used to simulate the direct radiative forcing. The calculations and results were obtained by applying a one- dimensional energy-balance box model. The influence of atmospheric aerosol on the sky brightness due to a total solar eclipse was studied using the photometric and meteorological observations made during the

  10. Overview of ACE-Asia Spring 2001 Investigations on Aerosol Radiative Effects and Related Aerosol Properties

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Valero, F. P. J.; Flatau, P. J.; Bergin, M.; Holben, B.; Nakajima, T.; Pilewskie, P.; Bergstrom, R.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    A primary, ACE-Asia objective was to quantify the interactions between aerosols and radiation in the Asia-Pacific region. Toward this end, radiometric and related aerosol measurements were made from ocean, land, air and space platforms. Models that predict aerosol fields guided the measurements and are helping integrate and interpret results. Companion overview's survey these measurement and modeling components. Here we illustrate how these components were combined to determine aerosol radiative. impacts and their relation to aerosol properties. Because clouds can obscure or change aerosol direct radiative effects, aircraft and ship sorties to measure these effects depended on predicting and finding cloud-free areas and times with interesting aerosols present. Pre-experiment satellite cloud climatologies, pre-flight aerosol and cloud forecasts, and in-flight guidance from satellite imagery all helped achieve this. Assessments of aerosol regional radiative impacts benefit from the spatiotemporal coverage of satellites, provided satellite-retrieved aerosol properties are accurate. Therefore, ACE-Asia included satellite retrieval tests, as part of many comparisons to judge the consistency (closure) among, diverse measurements. Early results include: (1) Solar spectrally resolved and broadband irradiances and optical depth measurements from the C-130 aircraft and at Kosan, Korea yielded aerosol radiative forcing efficiencies, permitting comparisons between efficiencies of ACE-Asia and INDOEX aerosols, and between dust and "pollution" aerosols. Detailed results will be presented in separate papers. (2) Based on measurements of wavelength dependent aerosol optical depth (AOD) and single scattering albedo the estimated 24-h a average aerosol radiative forcing efficiency at the surface for photosynthetically active radiation (400 - 700 nm) in Yulin, China is approx. 30 W sq m per AOD(500 nm). (3) The R/V Brown cruise from Honolulu to Sea of Japan sampled an aerosol optical

  11. Updating CMAQ secondary organic aerosol properties relevant for aerosol water interactions

    EPA Science Inventory

    Properties of secondary organic aerosol (SOA) compounds in CMAQ are updated with state-of-the-science estimates from structure activity relationships to provide consistency among volatility, molecular weight, degree of oxygenation, and solubility/hygroscopicity. These updated pro...

  12. Scattering and Absorption of E&M radiation by small particles-applications to study impact of biomass aerosols on climate

    NASA Astrophysics Data System (ADS)

    Bililign, Solomon; Singh, Sujeeta; Fiddler, Marc; Smith, Damon

    2015-03-01

    The phenomena of scattering, absorption, and emission of light and other electromagnetic radiation by small particles are central to many science and engineering disciplines. Absorption of solar radiation by black carbon aerosols has a significant impact on the atmospheric energy distribution and hydrologic processes. By intercepting incoming solar radiation before it reaches the surface, aerosols heat the atmosphere and, in turn, cool the surface. The magnitude of the atmospheric forcing induced by anthropogenic absorbing aerosols, mainly black carbon (BC) emitted from biomass burning and combustion processes has been suggested to be comparable to the atmospheric forcing by all greenhouse gases (GHGs). Despite the global abundance of biomass burning for cooking, forests clearing for agriculture and wild fires, the optical properties of these aerosols have not been characterized at wide range of wavelengths. Our laboratory uses a combination of Cavity ring down spectroscopy and integrating nephelometry to measure optical properties of (extinction, absorption and scattering coefficients) of biomass aerosols. Preliminary results will be presented. Supported by the Department of Defense under Grant #W911NF-11-1-0188.

  13. Quantitative retrieval of aerosol optical properties by means of ceilometers

    NASA Astrophysics Data System (ADS)

    Wiegner, Matthias; Gasteiger, Josef; Geiß, Alexander

    2016-04-01

    In the last few years extended networks of ceilometers have been established by several national weather services. Based on improvements of the hardware performance of these single-wavelength backscatter lidars and their 24/7 availability they are increasingly used to monitor mixing layer heights and to derive profiles of the particle backscatter profile. As a consequence they are used for a wide range of applications including the dispersion of volcanic ash plumes, validation of chemistry transport models and air quality studies. In this context the development of automated schemes to detect aerosol layers and to identify the mixing layer are essential, in particular as the latter is often used as a proxy for air quality. Of equal importance is the calibration of ceilometer signals as a pre-requisite to derive quantitative optical properties. Recently, it has been emphasized that the majority of ceilometers are influenced by water vapor absorption as they operate in the spectral range of 905 - 910 nm. If this effect is ignored, errors of the aerosol backscatter coefficient can be as large as 50%, depending on the atmospheric water vapor content and the emitted wavelength spectrum. As a consequence, any other derived quantity, e.g. the extinction coefficient or mass concentration, would suffer from a significant uncertainty in addition to the inherent errors of the inversion of the lidar equation itself. This can be crucial when ceilometer derived profiles shall be used to validate transport models. In this presentation, the methodology proposed by Wiegner and Gasteiger (2015) to correct for water vapor absorption is introduced and discussed.

  14. Satellite-Based Evidence of Wavelength-Dependent Aerosol Absorption in Biomass Burning Smoke Inferred from Ozone Monitoring Instrument

    NASA Technical Reports Server (NTRS)

    Jethva, H.; Torres, O.

    2012-01-01

    We provide satellite-based evidence of the spectral dependence of absorption in biomass burning aerosols over South America using near-UV measurements made by the Ozone Monitoring Instrument (OMI) during 2005-2007. In the current near-UV OMI aerosol algorithm (OMAERUV), it is implicitly assumed that the only absorbing component in carbonaceous aerosols is black carbon whose imaginary component of the refractive index is wavelength independent. With this assumption, OMI-derived aerosol optical depth (AOD) is found to be significantly over-estimated compared to that of AERONET at several sites during intense biomass burning events (August-September). Other well-known sources of error affecting the near-UV method of aerosol retrieval do not explain the large observed AOD discrepancies between the satellite and the ground-based observations. A number of studies have revealed strong spectral dependence in carbonaceous aerosol absorption in the near-UV region suggesting the presence of organic carbon in biomass burning generated aerosols. A sensitivity analysis examining the importance of accounting for the presence of wavelength-dependent aerosol absorption in carbonaceous particles in satellite-based remote sensing was carried out in this work. The results convincingly show that the inclusion of spectrally-dependent aerosol absorption in the radiative transfer calculations leads to a more accurate characterization of the atmospheric load of carbonaceous aerosols.

  15. The Microphysical and Chemical properties of aerosol particles from the United Arab Emirates Unified Aerosol Experiment (UAE2) and from the Bodele-BODEX Experiment

    NASA Astrophysics Data System (ADS)

    Martins, J.; Chaudhry, Z.; Todd, M.; Kaufman, Y.; Artaxo, P.

    2005-12-01

    Aerosol filters collected during the UAE2 experiment (August 2004), and during the BODEX experiment (in the Bodele region, February 2005) were analyzed for spectral absorption properties (from 350-2500nm), mass concentration (fine and coarse modes), electron microscopy, and chemical composition. The UAE2 samples show evidence of absorption by dust and urban pollution particles. In the fine mode, the urban pollution particles show spectral dependence inversely proportional to the wavelength, which is compatible with small black carbon aerosols. The coarse mode shows evidences of the internal mixture between dust and pollution, producing the typical strong absorption in UV-Visible wavelengths produced by dust, as well as significant absorption in the NIR (near infrared) coming from the dust-pollution combination. On the other hand, the Bodele samples show at least two types of dust absorption behavior: 1 - very strong absorption efficiency in the UV and visible wavelengths with nearly no absorption in the NIR; 2 - very strong absorption efficiency in the UV-VIS region with significant absorption in the NIR. Additional samples collected in the Amazon region, in Brazil, show evidence of long-range transport of dust from the Sahara. The chemical composition and microphysical properties of the Amazon Samples are compared with those measured in the UAE and Bodele regions. The chemical composition of these samples provides additional insight on previous theories of the fertilization of the Amazon by long-range transport of dust from the Sahara region.

  16. A Global Survey of Shipboard Measurements of Aerosol Optical Properties over the Oceans

    NASA Astrophysics Data System (ADS)

    Miller, M. A.; Reynolds, R. M.; Quinn, P.; Bartholomew, M. J.

    2001-12-01

    Marine aerosols contribute to the global albedo in two ways: direct scattering of incoming solar radiation to space (the direct effect) and modulation of the scattering properties of marine clouds (the indirect effect). The shortwave scattering and absorption characteristics of the marine atmosphere vary widely in space and time due to the variety of aerosol types, aerosol concentrations, and cloud structures that can be present. Aerosols over the oceans may originate from a variety of sources. Some are locally produced by wind-wave interaction while others are advected over great distances by the wind. In clear skies, advected continental aerosols can have a significantly different radiative impact than those that are locally produced. In cloudy skies, continental aerosol can cause modifications to the cloud droplet distribution in marine boundary layer clouds. Therefore, it is important to understand the spatial, temporal, and physical characteristics of aerosol over the world's oceans. Although information about aerosol optical properties over the world's oceans is critical, shipboard sun photometer measurements of these properties are relatively sparse. As part of our NASA SIMBIOS work and with additional support from the Department of Energy's (DOE) Atmospheric Radiation Program (ARM) program, the number of shipboard measurements has increased exponentially due to the development of a marine version of the Fast-Rotating, Shadow-band spectral Radiometer (FRSR). This instrument makes continuous, semi-automated shipboard measurements of the direct-normal, diffuse, and global irradiance in seven channels (415 nm, 500 nm, 610 nm, 660 nm, 862 nm, 936 nm, and broadband) and does not require a mechanically stabilized platform, thereby making it cost effective and reliable. The aerosol optical thickness is computed continuously from the direct-normal component of irradiance using calibration constants obtained using the Langley technique. The FRSR has been deployed on

  17. Estimating aerosol light-scattering enhancement from dry aerosol optical properties at different sites

    NASA Astrophysics Data System (ADS)

    Titos, Gloria; Jefferson, Anne; Sheridan, Patrick; Andrews, Elisabeth; Lyamani, Hassan; Ogren, John; Alados-Arboledas, Lucas

    2014-05-01

    Microphysical and optical properties of aerosol particles are strongly dependent on the relative humidity (RH). Knowledge of the effect of RH on aerosol optical properties is of great importance for climate forcing calculations and for comparison of in-situ measurements with satellite and remote sensing retrievals. The scattering enhancement factor, f(RH), is defined as the ratio of the scattering coefficient at a high and reference RH. Predictive capability of f(RH) for use in climate models would be enhanced if other aerosol parameters could be used as proxies to estimate hygroscopic growth. Toward this goal, we explore the relationship between aerosol light-scattering enhancement and dry aerosol optical properties such as the single scattering albedo (SSA) and the scattering Ångström exponent (SAE) at multiple sites around the world. The measurements used in this study were conducted by the US Department of Energy at sites where different aerosol types predominate (pristine marine, polluted marine, dust dominated, agricultural and forest environments, among others). In all cases, the scattering enhancement decreases as the SSA decreases, that is, as the contribution of absorbing particles increases. On the other hand, for marine influenced environments the scattering enhancement clearly increases as the contribution of coarse particles increases (SAE decreases), evidence of the influence of hygroscopic coarse sea salt particles. For other aerosol types the relationship between f(RH) and SAE is not so straightforward. Combining all datasets, f(RH) was found to exponentially increase with SSA with a high correlation coefficient.

  18. Sunphotometer network for monitoring aerosol properties in the Brazilian Amazon

    NASA Technical Reports Server (NTRS)

    Holben, Brent N.; Eck, T. F.; Setzer, A.; Pereira, Alfredo; Vermote, E.; Reagan, J. A.; Kaufman, Y. A.; Tanre, D.; Slutsker, I.

    1993-01-01

    Satellite platforms have provided a methodology for regional and global remote sensing of aerosols. New systems will significantly improve that capability during the EOS era; however, the voluminous 20 year record of satellite data has produced only regional snapshots of aerosol loading and have not yielded a data base of the optical properties of those aerosols which are fundamental to our understanding of their influence on climate change. The prospect of fully understanding the properties of the aerosols with respect to climate change is small without validation and augmentation by ancillary ground based observations. Sun photometry was demonstrated to be an effective tool for ground based measurements of aerosol optical properties from fire emissions. Newer technology has expanded routine sun photometer measurements to spectral observations of solar aureole and almucantar allowing retrievals of size distribution, scattering phase function, and refractive index. A series of such observations were made in Brazil's Amazon basin from a network of six simultaneously recording instruments deployed in Sep. 1992. The instruments were located in areas removed from local aerosol sources such that sites are representative of regional aerosol conditions. The overall network was designed to cover the counter clockwise tropospheric circulation of the Amazon Basin. Spectral measurements of sun, aureole and sky data for retrieval of aerosol optical thickness, particle size distribution, and scattering phase function as well as measurements of precipitable water were made during noncloudy conditions.

  19. Aerosol physical, chemical and optical properties observed in the ambient atmosphere during haze pollution conditions

    NASA Astrophysics Data System (ADS)

    Li, Zhengqiang; Xie, Yisong; Li, Donghui; Li, Kaitao; Zhang, Ying; Li, Li; Lv, Yang; Qie, Lili; Xu, Hua

    Aerosol’s properties in the ambient atmosphere may differ significantly from sampling results due to containing of abundant water content. We performed sun-sky radiometer measurements in Beijing during 2011 and 2012 winter to obtain distribution of spectral and angular sky radiance. The measurements are then used to retrieve aerosol physical, chemical and optical properties, including single scattering albedo, size distribution, complex refractive indices and aerosol component fractions identified as black carbon, brown carbon, mineral dust, ammonium sulfate-like components and water content inside particle matters. We found that during winter haze condition aerosol is dominated by fine particles with center radius of about 0.2 micron. Fine particles contribute about 93% to total aerosol extinction of solar light, and result in serious decrease of atmospheric visibility during haze condition. The percentage of light absorption of haze aerosol can up to about 10% among its total extinction, much higher than that of unpolluted conditions, that causes significant radiative cooling effects suppressing atmospheric convection and dispersion of pollutants. Moreover, the average water content occupies about one third of the ambient aerosol in volume which suggests the important effect of ambient humidity in the formation of haze pollution.

  20. Uncertainties of simulated aerosol optical properties induced by assumptions on aerosol physical and chemical properties: an AQMEII-2 perspective

    EPA Science Inventory

    The calculation of aerosol optical properties from aerosol mass is a process subject to uncertainty related to necessary assumptions on the treatment of the chemical species mixing state, density, refractive index, and hygroscopic growth. In the framework of the AQMEII-2 model in...

  1. Physico-chemical properties of aerosols in Sao Paulo, Brazil and mechanisms of secondary organic aerosol formation.

    NASA Astrophysics Data System (ADS)

    Artaxo, Paulo; Ferreira de Brito, Joel; Varanda Rizzo, Luciana; Luiza Godoy, Maria; Godoy, Jose Marcus

    2013-04-01

    Megacities emissions are increasingly becoming a global issue, where emissions from the transportation sector play an increasingly important role. Sao Paulo is a megacity with a population of about 18 million people, 7 million cars and large-scale industrial emissions. As a result of the vehicular and industrial emissions, the air quality in Sao Paulo is bellow WMO standards for aerosol particles and ozone. Many uncertainties are found on gas- and particulate matter vehicular emission factors and their following atmospheric processes, e.g. secondary organic aerosol formation. Due to the uniqueness of the vehicular fuel in Brazil, largely based on ethanol use, such characterization currently holds further uncertainties. To improve the understanding of the role of this unique emission characteristics, we are running a source apportionment study in Sao Paulo focused on the mechanisms of organic aerosol formation. One of the goals of this study is a quantitative aerosol source apportionment focused on vehicular emissions, including ethanol and gasohol (both fuels used by light-duty vehicles). This study comprises four sampling sites with continuous measurements for one year, where trace elements and organic aerosol are being measured for PM2.5 and PM10 along with real-time NOx, O3, PM10 and CO measurements. Aerosol optical properties and size distribution are being measured on a rotation basis between sampling stations. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to measure in real time VOCs and aerosol composition, respectively. Trace elements were measured using XRF and OC/EC analysis was determined with a Sunset OC/EC instrument. A TSI Nephelometer with 3 wavelengths measure light scattering and a MAAP measure black carbon. Results show aerosol number concentrations ranging between 10,000 and 35,000 cm-3, mostly concentrated in the nucleation and Aitken modes, with a peak in size at 80

  2. Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds

    SciTech Connect

    Turner, David, D.; Ferrare, Richard, A.

    2011-07-06

    The 'Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds' project focused extensively on the analysis and utilization of water vapor and aerosol profiles derived from the ARM Raman lidar at the Southern Great Plains ARM site. A wide range of different tasks were performed during this project, all of which improved quality of the data products derived from the lidar or advanced the understanding of atmospheric processes over the site. These activities included: upgrading the Raman lidar to improve its sensitivity; participating in field experiments to validate the lidar aerosol and water vapor retrievals; using the lidar aerosol profiles to evaluate the accuracy of the vertical distribution of aerosols in global aerosol model simulations; examining the correlation between relative humidity and aerosol extinction, and how these change, due to horizontal distance away from cumulus clouds; inferring boundary layer turbulence structure in convective boundary layers from the high-time-resolution lidar water vapor measurements; retrieving cumulus entrainment rates in boundary layer cumulus clouds; and participating in a field experiment that provided data to help validate both the entrainment rate retrievals and the turbulent profiles derived from lidar observations.

  3. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    NASA Astrophysics Data System (ADS)

    Pistone, K.; Praveen, P. S.; Thomas, R. M.; Ramanathan, V.; Wilcox, E.; Bender, F. A.-M.

    2015-10-01

    There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood, as changes in atmospheric conditions due to aerosol may change the expected magnitude of indirect effects by altering cloud properties in unexpected ways. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season. In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements of atmospheric precipitable water vapor and the liquid water path (LWP) of trade cumulus clouds were made, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol. Here we present evidence of a positive correlation between aerosol and cloud LWP which becomes clear after the data are filtered to control for the natural meteorological variability in the region. We then use the aircraft and ground observatory measurements to explore the mechanisms behind the observed aerosol-LWP correlation. We determine that increased boundary-layer humidity lowering the cloud base is responsible for the observed increase in cloud liquid water. Large-scale analysis indicates that high pollution cases originate with a highly-polluted boundary layer air mass approaching the observatory from a northwesterly direction. This polluted mass exhibits higher temperatures and humidity than the clean case, the former of which may be attributable to heating due to aerosol absorption of solar radiation over the subcontinent. While high temperature conditions dispersed along with the high-aerosol

  4. Synergy of Satellite-Surface Observations for Studying the Properties of Absorbing Aerosols in Asia

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee

    2010-01-01

    , in major international research projects such as the Joint Aerosol Monsoon Experiment (JAM EX), a core element of the Asian Monsoon Years (AMY, 2008-2012). SMART-COMMIT deployments during 2008 AMY/JAMEX were conducted in northwestern China to characterize the properties of dust-laden aerosols and in the vicinity of Beijing for mega-city aerosols. In 2009, SMART-COMMIT also participated in the JAMEX/RAJO-MEGHA (Radiation, Aerosol Joint Observations-Monsoon Experiment in the Gangetic-Himalayan Area; Sanskrit for Dust-Cloud) to study the aerosol properties, solar absorption and the associated atmospheric warming, and the climatic impact of elevated aerosols during the pre-monsoon season in South Asia. We will show results from these field experiments, as well as discuss a new initiative of 7-SEAS (7 South East Asian Studies) to study the interaction of anthropogenic aerosols with regional meteorology, particularly with clouds.

  5. Aerosol physical properties and their impact on climate change processes

    NASA Astrophysics Data System (ADS)

    Strzalkowska, Agata; Zielinski, Tymon; Petelski, Tomasz; Makuch, Przemyslaw; Pakszys, Paulina; Markuszewski, Piotr; Piskozub, Jacek; Drozdowska, Violetta; Gutowska, Dorota; Rozwadowska, Anna

    2013-04-01

    Characterizing aerosols involves the specification of not only their spatial and temporal distributions but their multi-component composition, particle size distribution and physical properties as well. Due to their light attenuation and scattering properties, aerosols influence radiance measured by satellite for ocean color remote sensing. Studies of marine aerosol production and transport are important for many earth sciences such as cloud physics, atmospheric optics, environmental pollution studies, and interaction between ocean and atmosphere. It was one of the reasons for the growth in the number of research programs dealing with marine aerosols. Sea salt aerosols are among the most abundant components of the atmospheric aerosol, and thus it exerts a strong influence on radiation, cloud formation, meteorology and chemistry of the marine atmosphere. An accurate understanding and description of these mechanisms is crucial to modeling climate and climate change. This work provides information on combined aerosol studies made with lidars and sun photometers onboard the ship and in different coastal areas. We concentrate on aerosol optical thickness and its variations with aerosol advections into the study area. We pay special attention to the problem of proper data collection and analyses techniques. We showed that in order to detect the dynamics of potential aerosol composition changes it is necessary to use data from different stations where measurements are made using the same techniques. The combination of such information with air mass back-trajectories and data collected at stations located on the route of air masses provides comprehensive picture of aerosol variations in the study area both vertically and horizontally. Acknowledgements: The support for this study was provided by the project Satellite Monitoring of the Baltic Sea Environment - SatBałtyk founded by European Union through European Regional Development Fund contract No. POIG 01

  6. Absorption of Visible and Long-wave Radiation by Primary and Secondary Biogenic Aerosols.

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.

    2008-12-01

    Field results for the 14C content of carbonaceous aerosols are presented that indicate significant biogenic sources of both primary and secondary aerosols in urban and regional environments. Samples collected in Mexico City and downwind of the urban area during the MILAGRO field study are compared with results reported previously in the literature indicating a significant amount of biogenic aerosols from both biomass burning and secondary photochemical production (e.g. terpene oxidations) are contributing to the overall carbonaceous aerosols in the optically active region of 0.1 to 1.0 micron. Samples in this size range collected on quartz fiber filters were also examined using an integrating sphere and FTIR diffuse reflectance techniques to obtain absorption spectra from 280 to the mid-IR. These data clearly indicate that the biogenic derived primary aerosols from agricultural and trash-burning, as well as secondary organic aerosols from isoprene and terpene oxidations will produce both UV-Visible (short-wave) absorbing substances as well as IR (long-wave) absorbing compounds including humic-like-substances (HULIS). With the anticipated increases in growing seasons (i.e. earlier springs and longer summers) the likely hood of increased fires (forest and grassland) as well as the continuing growth in agricultural burning activities, these primary sources are expected to increase and may play a role in heating of the atmosphere. The compound effects of these primary and secondary biogenic sources of absorbing aerosols to the total aerosol loading and regional climate will be discussed. This work was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64328 as part of the Atmospheric Science Program.

  7. Aerosol physical properties in the stratosphere (APPS) radiometer design

    NASA Technical Reports Server (NTRS)

    Gray, C. R.; Woodin, E. A.; Anderson, T. J.; Magee, R. J.; Karthas, G. W.

    1977-01-01

    The measurement concepts and radiometer design developed to obtain earth-limb spectral radiance measurements for the Aerosol Physical Properties in the Stratosphere (APPS) measurement program are presented. The measurements made by a radiometer of this design can be inverted to yield vertical profiles of Rayleigh scatterers, ozone, nitrogen dioxide, aerosol extinction, and aerosol physical properties, including a Junge size-distribution parameter, and a real and imaginary index of refraction. The radiometer design provides the capacity for remote sensing of stratospheric constituents from space on platforms such as the space shuttle and satellites, and therefore provides for global measurements on a daily basis.

  8. An aerosol climatology for a rapidly growing arid region (southern Arizona): Major aerosol species and remotely sensed aerosol properties

    PubMed Central

    Sorooshian, Armin; Wonaschütz, Anna; Jarjour, Elias G.; Hashimoto, Bryce I.; Schichtel, Bret A.; Betterton, Eric A.

    2014-01-01

    This study reports a comprehensive characterization of atmospheric aerosol particle properties in relation to meteorological and back trajectory data in the southern Arizona region, which includes two of the fastest growing metropolitan areas in the United States (Phoenix and Tucson). Multiple data sets (MODIS, AERONET, OMI/TOMS, MISR, GOCART, ground-based aerosol measurements) are used to examine monthly trends in aerosol composition, aerosol optical depth (AOD), and aerosol size. Fine soil, sulfate, and organics dominate PM2.5 mass in the region. Dust strongly influences the region between March and July owing to the dry and hot meteorological conditions and back trajectory patterns. Because monsoon precipitation begins typically in July, dust levels decrease, while AOD, sulfate, and organic aerosol reach their maximum levels because of summertime photochemistry and monsoon moisture. Evidence points to biogenic volatile organic compounds being a significant source of secondary organic aerosol in this region. Biomass burning also is shown to be a major contributor to the carbonaceous aerosol budget in the region, leading to enhanced organic and elemental carbon levels aloft at a sky-island site north of Tucson (Mt. Lemmon). Phoenix exhibits different monthly trends for aerosol components in comparison with the other sites owing to the strong influence of fossil carbon and anthropogenic dust. Trend analyses between 1988 and 2009 indicate that the strongest statistically significant trends are reductions in sulfate, elemental carbon, and organic carbon, and increases in fine soil during the spring (March–May) at select sites. These results can be explained by population growth, land-use changes, and improved source controls. PMID:24707452

  9. Enhanced UV Absorption in Carbonaceous Aerosols during MILAGRO and Identification of Potential Organic Contributors.

    NASA Astrophysics Data System (ADS)

    Mangu, A.; Kelley, K. L.; Marchany-Rivera, A.; Kilaparty, S.; Gunawan, G.; Gaffney, J. S.; Marley, N. A.

    2007-12-01

    Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) during the month of March, 2006 by using a 7- channel aethalometer (Thermo-Anderson). These measurements, obtained at 370, 470, 520, 590, 660, 880, and 950 nm at a 5 minute time resolution, showed an enhanced absorption in the UV over that expected from carbon soot alone. Samples of fine atmospheric aerosols (less than 0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. The samples were collected on quartz fiber filters with high volume impactor samplers. The samples have been characterized for total carbon content (stable isotope ratio mass spectroscopy) and natural radionuclide tracers (210Pb, 210Po, 210Bi, 7Be, 13C, 14C, 40K, 15N). Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV-visible spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples (1). The continuous spectra also show an enhanced UV absorption over that expected from carbon soot and the general profiles are quite similar to those observed for humic and fulvic acids found as colloidal materials in surface and groundwaters (2), indicating the presence of humic-like substances (HULIS) in the fine aerosols. The spectra also show evidence of narrow band absorbers below 400 nm typical of polycyclic aromatics (PAH) and nitrated aromatic compounds. Spectra were also obtained on NIST standard diesel soot (SRM 2975), NIST standard air particulate matter (SRM 8785

  10. Aerosol optical, microphysical and radiative properties at regional background insular sites in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Sicard, Michaël; Barragan, Rubén; Dulac, François; Alados-Arboledas, Lucas; Mallet, Marc

    2016-09-01

    In the framework of the ChArMEx (the Chemistry-Aerosol Mediterranean Experiment; http://charmex.lsce.ipsl.fr/) program, the seasonal variability of the aerosol optical, microphysical and radiative properties derived from AERONET (Aerosol Robotic Network; http://aeronet.gsfc.nasa.gov/) is examined in two regional background insular sites in the western Mediterranean Basin: Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). A third site, Alborán (Alborán Island, Spain), with only a few months of data is considered for examining possible northeast-southwest (NE-SW) gradients of the aforementioned aerosol properties. The AERONET dataset is exclusively composed of level 2.0 inversion products available during the 5-year period 2011-2015. AERONET solar radiative fluxes are compared with ground- and satellite-based flux measurements. To the best of our knowledge this is the first time that AERONET fluxes are compared with measurements at the top of the atmosphere. Strong events (with an aerosol optical depth at 440 nm greater than 0.4) of long-range transport aerosols, one of the main drivers of the observed annual cycles and NE-SW gradients, are (1) mineral dust outbreaks predominant in spring and summer in the north and in summer in the south and (2) European pollution episodes predominant in autumn. A NE-SW gradient exists in the western Mediterranean Basin for the aerosol optical depth and especially its coarse-mode fraction, which all together produces a similar gradient for the aerosol direct radiative forcing. The aerosol fine mode is rather homogeneously distributed. Absorption properties are quite variable because of the many and different sources of anthropogenic particles in and around the western Mediterranean Basin: North African and European urban areas, the Iberian and Italian peninsulas, most forest fires and

  11. Satellite remote sensing of aerosol and cloud properties over Eurasia

    NASA Astrophysics Data System (ADS)

    Sogacheva, Larisa; Kolmonen, Pekka; Saponaro, Giulia; Virtanen, Timo; Rodriguez, Edith; Sundström, Anu-Maija; Atlaskina, Ksenia; de Leeuw, Gerrit

    2015-04-01

    Satellite remote sensing provides the spatial distribution of aerosol and cloud properties over a wide area. In our studies large data sets are used for statistical studies on aerosol and cloud interaction in an area over Fennoscandia, the Baltic Sea and adjacent regions over the European mainland. This area spans several regimes with different influences on aerosol cloud interaction such as a the transition from relative clean air over Fennoscandia to more anthropogenically polluted air further south, and the influence maritime air over the Baltic and oceanic air advected from the North Atlantic. Anthropogenic pollution occurs in several parts of the study area, and in particular near densely populated areas and megacities, but also in industrialized areas and areas with dense traffic. The aerosol in such areas is quite different from that produced over the boreal forest and has different effects on air quality and climate. Studies have been made on the effects of aerosols on air quality and on the radiation balance in China. The aim of the study is to study the effect of these different regimes on aerosol-cloud interaction using a large aerosol and cloud data set retrieved with the (Advanced) Along Track Scanning Radiometer (A)ATSR Dual View algorithm (ADV) further developed at Finnish Meteorological Institute and aerosol and cloud data provided by MODIS. Retrieval algorithms for aerosol and clouds have been developed for the (A)ATSR, consisting of a series of instruments of which we use the second and third one: ATSR-2 which flew on the ERS-2 satellite (1995-2003) and AATSR which flew on the ENVISAT satellite (2002-2012) (both from the European Space Agency, ESA). The ADV algorithm provides aerosol data on a global scale with a default resolution of 10x10km2 (L2) and an aggregate product on 1x1 degree (L3). Optional, a 1x1 km2 retrieval products is available over smaller areas for specific studies. Since for the retrieval of AOD no prior knowledge is needed on

  12. Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

    NASA Astrophysics Data System (ADS)

    Flores, J. Michel; Bar-Or, R. Z.; Bluvshtein, N.; Abo-Riziq, A.; Kostinski, A.; Borrmann, S.; Koren, I.; Koren, I.; Rudich, Y.

    2012-06-01

    One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. Aerosols exposed to high humidity will change their chemical, physical, and optical properties due to their increased water content. To model hydrated aerosols, atmospheric chemistry and climate models often use the volume weighted mixing rule to predict the complex refractive index (RI) of aerosols when they interact with high relative humidity, and, in general, assume homogeneous mixing. This study explores the validity of these assumptions. A humidified cavity ring down aerosol spectrometer (CRD-AS) and a tandem hygroscopic DMA (differential mobility analyzer) are used to measure the extinction coefficient and hygroscopic growth factors of humidified aerosols, respectively. The measurements are performed at 80% and 90%RH at wavelengths of 532 nm and 355 nm using size-selected aerosols with different degrees of absorption; from purely scattering to highly absorbing particles. The ratio of the humidified to the dry extinction coefficients (fRHext(%RH, Dry)) is measured and compared to theoretical calculations based on Mie theory. Using the measured hygroscopic growth factors and assuming homogeneous mixing, the expected RIs using the volume weighted mixing rule are compared to the RIs derived from the extinction measurements. We found a weak linear dependence or no dependence of fRH(%RH, Dry) with size for hydrated absorbing aerosols in contrast to the non-monotonically decreasing behavior with size for purely scattering aerosols. No discernible difference could be made between the two wavelengths used. Less than 7% differences were found between the real parts of the complex refractive indices derived and those calculated using the volume weighted mixing rule, and the imaginary parts had up to a 20% difference. However, for substances with growth factor less than 1.15 the volume weighted mixing rule assumption

  13. The analysis of in situ and retrieved aerosol properties measured during three airborne field campaigns

    NASA Astrophysics Data System (ADS)

    Corr, Chelsea A.

    Aerosols can directly influence climate, visibility, and photochemistry by scattering and absorbing solar radiation. Aerosol chemical and physical properties determine how efficiently a particle scatters and/or absorbs incoming short-wave solar radiation. Because many types of aerosol can act as nuclei for cloud droplets (CCN) and a smaller population of airborne particles facilitate ice crystal formation (IN), aerosols can also alter cloud-radiation interactions which have subsequent impacts on climate. Thus aerosol properties determine the magnitude and sign of both the direct and indirect impacts of aerosols on radiation-dependent Earth System processes. This dissertation will fill some gaps in our understanding of the role of aerosol properties on aerosol absorption and cloud formation. Specifically, the impact of aerosol oxidation on aerosol spectral (350nm < lambda< 500nm) absorption was examined for two biomass burning plumes intercepted by the NASA DC-S aircraft during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission in Spring and Summer 2008. Spectral aerosol single scattering albedo (SSA) retrieved using actinic flux measured aboard the NASA DC-8 was used to calculate the aerosol absorption Angstrom exponents (AAE) for a 6-day-old plume on April 17 th and a 3-hour old plume on June 29th. Higher AAE values for the April 17th plume (6.78+/-0.38) indicate absorption by aerosol was enhanced in the ultraviolet relative to the visible portion of the short-wave spectrum in the older plume compared to the fresher plume (AAE= 3.34 0.11). These differences were largely attributed to the greater oxidation of the organic aerosol in the April 17th plume which can arise either from the aging of primary organic aerosol or the formation of spectrally-absorbing secondary organic aerosol. The validity of the actinic flux retrievals used above were also evaluated in this work by the comparison of SSA retrieved using

  14. Influences of relative humidity on aerosol optical properties and aerosol radiative forcing during ACE-Asia

    NASA Astrophysics Data System (ADS)

    Yoon, Soon-Chang; Kim, Jiyoung

    In situ measurements at Gosan, South Korea, and onboard C-130 aircraft during ACE-Asia were analyzed to investigate the influence of relative humidity (RH) on aerosol optical properties and radiative forcing. The temporal variation of aerosol chemical composition at the Gosan super-site was highly dependent on the air mass transport pathways and source region. RH in the springtime over East Asia were distributed with very high spatial and temporal variation. The RH profile onboard C-130 aircraft measurements exhibits a mixed layer height of about 2 km. Aerosol scattering coefficient ( σsp) under ambient RH was greatly enhanced as compared with that at dry RH (RH<40%). From the aerosol optical and radiative transfer modeling studies, we found that the extinction and scattering coefficients are greatly enhanced with RH. Single scattering albedo with RH is also sensitively changed in the longer wavelength. Asymmetry parameter ( g) is gradually increased with RH although g decreases with wavelength at a given RH. Aerosol optical depth (AOD) at 550 nm and RH of 50% increased to factors 1.24, 1.51, 2.16, and 3.20 at different RH levels 70, 80, 90, and 95%, respectively. Diurnal-averaged aerosol radiative forcings for surface, TOA, and atmosphere were increased with RH because AOD was increased with RH due to hygroscopic growth of aerosol particles. This result implies that the hygroscopic growth due to water-soluble or hydrophilic particles in the lower troposphere may significantly modify the magnitude of aerosol radiative forcing both at the surface and TOA. However, the diurnal-averaged radiative forcing efficiencies at the surface, TOA, and atmosphere were decreased with increasing RH. The decrease of the forcing efficiency with RH results from the fact that increasing rate of aerosol optical depth with RH is greater than the increasing rate of aerosol radiative forcing with RH.

  15. A comparison between aerosol properties and air pollutants

    NASA Astrophysics Data System (ADS)

    Mukai, S.; Sano, I.; Nishimori, A.; Sato, M.

    A comparison between aerosol properties and air pollutants over urban cities in Japan S. Mukai, I. Sano, A. Nishimori and M. Sato Kinki University For understanding urban aerosols, sun/sky photometry and polarimetry with PSR-1000 (Opto. Research) have been undertaken over Higashi-Osaka since 1996. Multi-spectral photometers CE-318 (Cimel Electronique) and POM-100P (Prede Co.) are set up later for an AERONET site and a SKYNET site, respectively. Radiometers provide us with the optical thickness of aerosols and Ångström exponent. Another aerosol properties, e.g., size distribution, refractive index, etc., are retrieved based on the inversion method. Higashi-Osaka, which means east side of Osaka, is an industrial city located between Osaka bay and Mt.Ikoma. Anthropogenic aerosols produced by industrial activity and oceanic aerosols flying from Osaka bay are mixed together and trapped just around our site due to reflection from Mt.Ikoma. Therefore our city is famous for heavy air pollution, and aerosols here have a complicated feature mixing with the anthropogenic compound and natural one externally and/or internally. On the other hand, suspended particles matter (SPM) concentrations at ground level are compiled for these 10 years in this city. Strictly speaking, it is difficult to relate SPM data directly to the aerosol properties, however it is possible to say that SPM data represents the mass concentration of atmospheric particles at ground level. In other word, air pollutants could have some relations to the emission and transportation of aerosols. After several aerosol parameters are derived from the measurements and compared with the SPM data, the HYSPLIT4 backward trajectory analysis is adopted to search the origin of atmospheric particles. It is found that aerosol index shows a proportional correlation with SPM concentration, and that our aerosols are contaminated not only by surroundings but also the large scale phenomena, e.g. yellow sand event from China

  16. Aerosol Physical and Chemical Properties Before and After the Manaus Plume in the GoAmazon2014 Experiment

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Barbosa, H. M.; Ferreira De Brito, J.; Wurm, F.; Holanda, B. A.; Carbone, S.; Arana, A.; Cirino, G. G.; Souza, R. A. F. D.; Rizzo, L. V.; Martin, S. T.; Andreae, M. O.; Holben, B. N.; Schafer, J.

    2014-12-01

    As part of the GoAmazon2014 experiment, several aerosol and trace gas monitoring stations are being operated for at least one year before and after the Manaus plume. Three sites are being operated in pristine conditions, with atmospheric properties under natural biogenic conditions. These three sites called T0 are: ATTO (Amazon Tall Tower Observatory), ZF2 ecological research site and a third site called EMBRAPA. After the air masses are exposed to the Manaus plume, one site (called T2) is being operated right on the opposite side of the Negro River under the direct influence of the Manaus plume at 5 Km downwind of Manaus. Finally, at about 150 Km downwind of Manaus is the T3 Manacapuru site. Aerosol chemical composition is being analyzed using filters for fine (PM2.5) and coarse mode aerosol as well as three Aerodyne ACSM (Aerosol Chemical Speciation Monitors) instruments. Aerosol absorption is being studied with several aethalometers and MAAP (Multi Angle Absorption Photometers). Aerosol light scattering are being measured at several wavelengths using nephelometers. Aerosol size distribution is determined using scanning mobility particle sizers. The aerosol column is measures using AERONET sunphotometers before and after the Manaus plume, as well as several Lidar systems. The three sites before the Manaus plume show remarkable similar variability in aerosol concentrations and optical properties. This pattern is very different at the T2 site, with large aerosol concentrations enhancing aerosol absorption and scattering significantly. The aerosol is very oxidized before being exposed to the Manaus plume, and this pattern changes significantly for T2 and T3 sites, with a much higher presence of less oxidized aerosol. Typical ozone concentrations at mid-day before Manaus plume is a low 10-12 ppb, value that changes to 50-70 ppb for air masses suffering the influence of Manaus plume. A detailed comparison of aerosol characteristics and composition for the several

  17. Evaluation of the effects of Mount Pinatubo aerosol on differential absorption lidar measurements of stratospheric ozone

    SciTech Connect

    Steinbrecht, W.; Carswell, A.I.

    1995-01-01

    Substantially increased aerosol backscattering and extinction after a major volcanic eruption can lead to errors in differential absorption lidar (DIAL) measurements of stratospheric ozone. Mie calculations, performed for the wavelengths 308 and 353 nm and based on size distributions measured over Laramie, Wyoming (41 deg), were used to assess size and temporal evolution of these errors. In many situations, neglecting the different aerosol backscattering at the absorption and reference wavelengths can lead to relative errors in the ozone concentration larger than 100% for the 308-, 353-nm pair. The error due to neglecting the differential aerosol extinction, however, will rarely exceed 2%. A correction for this differential extinction should only be attempted when high concentrations (greater than 100/cu cm) of small aerosol particles with radii below 0.1 micrometers are present, e.g., shortly after an eruption. A correction for the differential backscatter can be made by using additional lidar measurements at a second reference wavelength or by having general size distribution information on the aerosol. Possible corrections were tested and will usually reduce the error in the ozone concentration considerably. For the 308-, 353-nm pair, both Mie calculations and a comparison with ozone profiles from electrochemical cell sondes show, however, that even after the correction the uncertainty in the ozone concentration within some regions of the strongly enhanced Mt. Pinatubo aerosol layer can still be substantial, of the order of 10-50%. Wavelength separation smaller than 40 nm or use of wavelengths shorter than 300 nm will reduce the error. The best solution seems to be the addition of Raman channels. It avoids the large error due to the differential backscatter term.

  18. Airborne Lidar Measurements of Aerosol Optical Properties During SAFARI-2000

    NASA Technical Reports Server (NTRS)

    McGill, M. J.; Hlavka, D. L.; Hart, W. D.; Welton, E. J.; Campbell, J. R.; Starr, David OC. (Technical Monitor)

    2002-01-01

    The Cloud Physics Lidar (CPL) operated onboard the NASA ER-2 high altitude aircraft during the SAFARI-2000 field campaign. The CPL provided high spatial resolution measurements of aerosol optical properties at both 1064 nm and 532 nm. We present here results of planetary boundary layer (PBL) aerosol optical depth analysis and profiles of aerosol extinction. Variation of optical depth and extinction are examined as a function of regional location. The wide-scale aerosol mapping obtained by the CPL is a unique data set that will aid in future studies of aerosol transport. Comparisons between the airborne CPL and ground-based MicroPulse Lidar Network (MPL-Net) sites are shown to have good agreement.

  19. Aerosol properties derived from spectral actinic flux measurements

    NASA Astrophysics Data System (ADS)

    Stark, H.; Schmidt, K. S.; Pilewskie, P.; Cozic, J.; Wollny, A. G.; Brock, C. A.; Baynard, T.; Lack, D.; Parrish, D. D.; Fehsenfeld, F. C.

    2008-12-01

    Measurement of aerosol properties is very important for understanding climate change. Aerosol optical properties influence solar radiation throughout the troposphere. According to the Working Group I report of the intergovernmental panel for climate change [IPCC, 2007], aerosols have a direct radiative forcing of - 0.5±0.4 W/m2 with a medium to low level of scientific understanding. This relatively large uncertainty indicates the need for more frequent and precise measurements of aerosol properties. We will show how actinic flux measurements can be used to derive important optical aerosol parameters such as aerosol optical thickness and depth, surface albedo, angstrom exponent, radiative forcing by clouds and aerosols, aerosol extinction, and others. The instrument used for this study is a combination of two spectroradiometers measuring actinic flux in the ultraviolet and visible radiation range from 280 to 690 nm with a resolution of 1 nm. Actinic flux is measured as the radiation incident on a spherical surface with sensitivity independent of direction. In contrast, irradiance is measured as the radiation incident on a plane surface, which depends on the cosine of the incident angle. Our goal is to assess the capabilities of using spectral actinic flux measurements to derive various aerosol properties. Here we will compare 1) actinic flux measurements to irradiance measurements from the spectral solar flux radiometer (SSFR), 2) derived aerosol size distributions with measurements from a white light optical particle counter (WLOPC) and ultra high sensitivity aerosol size spectrometer (UHSAS), and 3) derived aerosol optical extinction with measurements from a cavity ringdown aerosol extinction spectrometer (CRD-AES). These comparisons will utilize data from three recent field campaigns over New England and the Atlantic Ocean (ICARTT 2004), Texas and the Gulf of Mexico during (TexAQS/GoMACCS 2006), and Alaska and the Arctic Ocean (ARCPAC 2008) when the instruments

  20. Comparison of experimental and modeled absorption enhancement by black carbon (BC) cored polydisperse aerosols under hygroscopic conditions.

    PubMed

    Shamjad, P M; Tripathi, S N; Aggarwal, S G; Mishra, S K; Joshi, Manish; Khan, Arshad; Sapra, B K; Ram, Kirpa

    2012-08-07

    The quantification of the radiative impacts of light absorbing ambient black carbon (BC) particles strongly depends on accurate measurements of BC mass concentration and absorption coefficient (β(abs)). In this study, an experiment has been conducted to quantify the influence of hygroscopic growth of ambient particles on light absorption. Using the hygroscopic growth factor (i.e., Zdanovskii-Stokes-Robinson (ZSR) approach), a model has been developed to predict the chemical composition of particles based on measurements, and the absorption and scattering coefficients are derived using a core-shell assumption with light extinction estimates based on Mie theory. The estimated optical properties agree within 7% for absorption coefficient and 30% for scattering coefficient with that of measured values. The enhancement of absorption is found to vary according to the thickness of the shell and BC mass, with a maximum of 2.3 for a shell thickness of 18 nm for the particles. The findings of this study underline the importance of considering aerosol-mixing states while calculating their radiative forcing.

  1. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    NASA Astrophysics Data System (ADS)

    Pistone, Kristina; Praveen, Puppala S.; Thomas, Rick M.; Ramanathan, Veerabhadran; Wilcox, Eric M.; Bender, Frida A.-M.

    2016-04-01

    There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric vertical structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season.In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements were made of atmospheric precipitable water vapor (PWV) and the liquid water path (LWP) of trade cumulus clouds, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol from instrumentation at a ground observatory and on small unmanned aircraft. We present observations which indicate a positive correlation between aerosol and cloud LWP only when considering cases with low atmospheric water vapor (PWV < 40 kg m-2), a criterion which acts to filter the data to control for the natural meteorological variability in the region.We then use the aircraft and ground-based measurements to explore possible mechanisms behind this observed aerosol-LWP correlation. The increase in cloud liquid water is found to coincide with a lowering of the cloud base, which is itself attributable to increased boundary layer humidity in polluted conditions. High pollution is found to correlate with both higher temperatures and higher humidity measured throughout the boundary layer. A large-scale analysis, using satellite observations and meteorological reanalysis, corroborates these covariations: high-pollution cases are shown to originate as a highly polluted boundary layer air mass approaching the observatory from a northwesterly

  2. Optical properties and CCN activity of aerosols in a high-altitude Himalayan environment: Results from RAWEX-GVAX

    NASA Astrophysics Data System (ADS)

    Gogoi, Mukunda M.; Babu, S. Suresh; Jayachandran, V.; Moorthy, K. Krishna; Satheesh, S. K.; Naja, Manish; Kotamarthi, V. R.

    2015-03-01

    The seasonality and mutual dependence of aerosol optical properties and cloud condensation nuclei (CCN) activity under varying meteorological conditions at the high-altitude Nainital site (~2 km) in the Indo-Gangetic Plains were examined using nearly year-round measurements (June 2011 to March 2012) at the Atmospheric Radiation Measurement mobile facility as part of the Regional Aerosol Warming Experiment-Ganges Valley Aerosol Experiment of the Indian Space Research Organization and the U.S. Department of Energy. The results from collocated measurements provided enhanced aerosol scattering and absorption coefficients, CCN concentrations, and total condensation nuclei concentrations during the dry autumn and winter months. The CCN concentration (at a supersaturation of 0.46) was higher during the periods of high aerosol absorption (single scattering albedo (SSA) < 0.80) than during the periods of high aerosol scattering (SSA > 0.85), indicating that the aerosol composition seasonally changes and influences the CCN activity. The monthly mean CCN activation ratio (at a supersaturation of 0.46) was highest (>0.7) in late autumn (November); this finding is attributed to the contribution of biomass-burning aerosols to CCN formation at high supersaturation conditions.

  3. Aerosol properties over south india during different seasons

    NASA Astrophysics Data System (ADS)

    Sivaprasad, P.; Babu, C. A.; Jayakrishnan, P. R.

    Aerosols play an important role in the radiation balance and cloud properties, thereby affect the entire climatology of the earth-atmosphere system. Besides natural sources like dust, seasalt and natural sulphates, anthropogenic activities also inject aerosols like soot and industrial sulphates. Of these sea-salt and sulphates scatter the solar radiation. Soot is an absorbing aerosol while soil dust and organic matters are partly absorbing aerosols. Wind and rainfall are major factors affecting the transportation and deposition of the aerosols. India is a country blessed with plenty of monsoon rains. Winter (December to February), summer (March to May), monsoon (June to September) and post monsoon (October to November) are the four seasons over the region. Aerosol properties vary according to the season. Natural aerosols blown from the deserts have a major role in the aerosol optical depth over India. Of this, dust from Arabian desert that is carried by the winds are most important. The aerosol optical depth of south India is entirely different from that of north India. Maximum aerosol concentration is found over Gangetic plane in most of the seasons, whereas entire south India shows less aerosol optical depth. In the present study the aerosol properties of south India is analysed in general. Particular analysis is carried out for the four regions in the east and west coasts around Chennai, Kolkotha, Mumbai and Cochin. Chennai and Kolkotha are situated in the east coast whereas Cochin and Mumbai are in the west coast. These are industrial cities in India. Chennai region does not get monsoon rainfall since it is situated in the leeward side of Western ghats. But in the post monsoon season Chennai gets good amount of rainfall. Other three regions get good amount of rainfall during monsoon season. The study uses Terra MODIS, TOMS, NCEP/NCAR and TRMM data. Aerosol properties are analysed using Terra MODIS and Nimbus TOMS data. The variations of the aerosol optical

  4. Airborne Sunphotometer Studies of Aerosol Properties and Effects, Including Closure Among Satellite, Suborbital Remote, and In situ Measurements

    NASA Technical Reports Server (NTRS)

    Russlee, Philip B.; Schmid, B.; Redemann, J.; Livingston, J. M.; Bergstrom, R. W.; Ramirez, S. A.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    Airborne sunphotometry has been used to measure aerosols from North America, Europe, and Africa in coordination with satellite and in situ measurements in TARFOX (1996), ACE-2 (1997), PRIDE (2000), and SAFARI 2000. Similar coordinated measurements of Asian aerosols are being conducted this spring in ACE-Asia and are planned for North American aerosols this summer in CLAMS. This paper summarizes the approaches used, key results, and implications for aerosol properties and effects, such as single scattering albedo and regional radiative forcing. The approaches exploit the three-dimensional mobility of airborne sunphotometry to access satellite scenes over diverse surfaces (including open ocean with and without sunglint) and to match exactly the atmospheric layers sampled by airborne in situ measurements and other radiometers. These measurements permit tests of the consistency, or closure, among such diverse measurements as aerosol size-resolved chemical composition; number or mass concentration; light extinction, absorption, and scattering (total, hemispheric back and 180 deg.); and radiative fluxes. In this way the airborne sunphotometer measurements provide a key link between satellite and in situ measurements that helps to understand any discrepancies that are found. These comparisons have led to several characteristic results. Typically these include: (1) Better agreement among different types of remote measurements than between remote and in situ measurements. (2) More extinction derived from transmission measurements than from in situ measurements. (3) Larger aerosol absorption inferred from flux radiometry than from in situ measurements. Aerosol intensive properties derived from these closure studies have been combined with satellite-retrieved fields of optical depth to produce fields of regional radiative forcing. We show results for the North Atlantic derived from AVHRR optical depths and aerosol intensive properties from TARFOX and ACE-2. Companion papers

  5. Optical, physical, and chemical properties of springtime aerosol over Barrow Alaska in 2008

    SciTech Connect

    Shantz, Nicole C.; Gultepe, Ismail; Andrews, Elisabeth; Earle, Michael; MacDonald, A. M.; Liu, Peter S.K.; Leaitch, W. R.

    2014-03-06

    Airborne observations from four flights during the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) are used to examine some cloud-free optical, physical, and chemical properties of aerosol particles in the springtime Arctic troposphere. The number concentrations of particles larger than 0.12 μm (Na>120), important for light extinction and cloud droplet formation, ranged from 15 to 2260 cm-3, with the higher Na>120 cases dominated by measurements from two flights of long-range transported biomass burning (BB) aerosols. The two other flights examined here document a relatively clean aerosol and an Arctic Haze aerosol impacted by larger particles largely composed of dust. For observations from the cleaner case and the BB cases, the particle light scattering coefficients at low relative humidity (RH<20%) increased nonlinearly with increasing Na>120, driven mostly by an increase in mean sizes of particles with increasing Na>120 (BB cases). For those three cases, particle light absorption coefficients also increased nonlinearly with increasing Na>120 and linearly with increasing submicron particle volume concentration. In addition to black carbon, brown carbon was estimated to have increased light absorption coefficients by 27% (450 nm wavelength) and 14% (550 nm) in the BB cases. For the case with strong dust influence, the absorption relative to submicron particle volume was small compared with the other cases. There was a slight gradient of Passive Cavity Aerosol Spectrometer Probe (PCASP) mean volume diameter (MVD) towards smaller sizes with increasing height, which suggests more scavenging of the more elevated particles, consistent with a typically longer lifetime of particles higher in the atmosphere. However, in approximately 10% of the cases, the MVD increased (>0.4 μm) with increasing altitude, suggesting transport of larger fine particle mass (possibly coarse particle mass) at high levels over the Arctic. This may be because of transport of

  6. Inversion Techniques for Retrieving Detailed Aerosol Properties from Remote Sensing Observations: Achievements and Perspectives

    NASA Astrophysics Data System (ADS)

    Dubovik, O.

    2010-12-01

    applications. Specifically, the retrieval of detailed information about aerosol particle sizes, shape, absorption and composition (refractive index) from the observations by sun/sky-scanning radiometers has been developed and employed by worldwide AERONET network of ground-based radiometers. One of first retrievals of global aerosol emission sources from MODIS satellite observations have been suggested and realized using the same concept. Finally, the most recent results show a high potential of applying the methodology for deriving aerosol properties over bright land surfaces from POLDER multi-angle spectral polarimetric satellite observations using a new approach of simultaneous inversion of large groups of satellite pixels.

  7. Investigation of the seasonal variations of aerosol physicochemical properties and their impact on cloud condensation nuclei number concentration

    NASA Astrophysics Data System (ADS)

    Logan, Timothy S.

    Aerosols are among the most complex yet widely studied components of the atmosphere not only due to the seasonal variability of their physical and chemical properties but also their effects on climate change. The three main aerosol types that are known to affect the physics and chemistry of the atmosphere are: mineral dust, anthropogenic pollution, and biomass burning aerosols. In order to understand how these aerosols affect the atmosphere, this dissertation addresses the following three scientific questions through a combination of surface and satellite observations: SQ1: What are the seasonal and regional variations of aerosol physico-chemical properties at four selected Asian sites? SQ2: How do these aerosol properties change during transpacific and intra-continental long range transport? SQ3: What are the impacts of aerosol properties on marine boundary layer cloud condensation nuclei number concentration? This dissertation uses an innovative approach to classify aerosol properties by region and season to address SQ1. This is useful because this method provides an additional dimension when investigating the physico-chemical properties of aerosols by linking a regional and seasonal dependence to both the aerosol direct and indirect effects. This method involves isolating the aerosol physico-chemical properties into four separate regions using AERONET retrieved Angstrom exponent (AEAOD) and single scattering co-albedo (o oabs) to denote aerosol size and absorptive properties. The aerosols events are then clustered by season. The method is first applied to four AERONET sites representing single mode aerosol dominant regions: weakly absorbing pollution (NASA Goddard), strongly absorbing pollution (Mexico City), mineral dust (Solar Village), and biomass burning smoke (Alta Floresta). The method is then applied to four Asian sites that represent complicated aerosol components. There are strong regional and seasonal influences of the four aerosol types over the

  8. Development of 2-D-MAX-DOAS and retrievals of trace gases and aerosols optical properties

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan

    Air pollution is a major problem worldwide that adversely a_ects human health, impacts ecosystems and climate. In the atmosphere, there are hundreds of important compounds participating in complex atmospheric reactions linked to air quality and climate. Aerosols are relevant because they modify the radiation balance, a_ect clouds, and thus Earth albedo. The amount of aerosol is often characterized by the vertical integral through the entire height of the atmosphere of the logarithm fraction of incident light that is extinguished called Aerosol Optical Depth (AOD). The AOD at 550 nm (AOD550) over land is 0.19 (multi annual global mean), and that over oceans is 0.13. About 43 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions, sample spatial scales that resemble satellite ground-pixels and atmospheric models, and help integrate remote sensing and in-situ observations to obtain optical closure on the effects of aerosols and trace gases in our changing environment. In this work, I present the recent development of the University of Colorado two dimensional (2-D) Multi-AXis Differential Optical Absorption Spectroscopy (2-D-MAX-DOAS) instrument to measure the azimuth and altitude distribution of trace gases and aerosol optical properties simultaneously with a single instrument. The instrument measures solar scattered light from any direction in the sky, including direct sun light in the hyperspectral domain. In Chapter 2, I describe the capabilities of 2-D measurements in the context of retrievals of azimuth distributions of nitrogen dioxide (NO2), formaldehyde (HCHO), and glyoxal (CHOCHO), which are precursors for tropospheric O3 and aerosols. The measurements were carried out during the Multi-Axis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) campaign in Mainz, Germany and show the ability to bridge spatial scales to

  9. Cloud Properties Derived from Visible and Near-infrared Reflectance in the Presence of Aerosols

    NASA Astrophysics Data System (ADS)

    Pilewskie, P.; Hofmann, O.; Kindel, B.; Gore, W.; Russell, P.; Livingston, J.; Redemann, J.; Bergstrom, R.; Platnick, S.; Daniel, J.; Garrett, T.

    2005-12-01

    The New England Air Quality Study - Intercontinental Transport and Chemical Transformation (NEAQS-ITCT) experiment conducted in July-August 2004 included objectives on the effects of urban-industrial pollution aerosols on cloud radiative properties, the so-called indirect effect. Measurements of spectral irradiance covering the near-ultraviolet to near-infrared were made from two airborne platforms, the NOAA WP-3D and the Sky Research J-31, using identical Solar Spectral Flux Radiometers (SSFR). The SSFR measured the upwelling and downwelling spectral irradiance between 380-1670 nm from which the spectral albedo (ratio of upwelling to downwelling) and net (difference between downwelling and upwelling) irradiance were derived. Cloud spectral albedo was used to retrieve cloud particle effective radius, optical depth, and liquid water path. The robustness of the optical retrieval method will be examined by comparing the WP-3D SSFR retrievals to in situ measurements made with an FSSP-100 and an OAP 2D-C and to an independent retrieval using Miniaturized Differential Absorption Spectroscopy (MIDAS), also on board the WP-3D. A sunphotometer was also deployed on the J-31, the14-channel NASA Ames Airborne Tracking Sunphotometer (AATS-14), providing aerosol optical depths at thirteen discrete wavelengths between 354-2138 nm. J-31 flights on 15, 20, and 31 July were of particular interest because AATS-14 data revealed the presence aerosol layers above clouds. Comparisons between SSFR-derived cloud properties and MODIS cloud retrievals were in close agreement when aerosol optical depth was less than 0.1. Over moderately thick clouds there is evidence that an enhanced aerosol layer, such as that encountered during the 20 July case, may affect the retrieved cloud properties. Such an influence must be distinguished from a true "aerosol indirect effect" in order to accurately quantify the amount by which aerosols modify cloud albedo.

  10. Aerosol-halogen interaction: Change of physico-chemical properties of SOA by naturally released halogen species

    NASA Astrophysics Data System (ADS)

    Ofner, J.; Balzer, N.; Buxmann, J.; Grothe, H.; Krüger, H.; Platt, U.; Schmitt-Kopplin, P.; Zetzsch, C.

    2011-12-01

    Reactive halogen species are released by various sources like photo-activated sea-salt aerosol or salt pans and salt lakes. These heterogeneous release mechanisms have been overlooked so far, although their potential of interaction with organic aerosols like Secondary Organic Aerosol (SOA), Biomass Burning Organic Aerosol (BBOA) or Atmospheric Humic LIke Substances (HULIS) is completely unknown. Such reactions can constitute sources of gaseous organo-halogen compounds or halogenated organic particles in the atmospheric boundary layer. To study the interaction of organic aerosols with reactive halogen species (RHS), SOA was produced from α-pinene, catechol and guaiacol using an aerosol smog-chamber. The model SOAs were characterized in detail using a variety of physico-chemical methods (Ofner et al., 2011). Those aerosols were exposed to molecular halogens in the presence of UV/VIS irradiation and to halogens, released from simulated natural halogen sources like salt pans, in order to study the complex aerosol-halogen interaction. The heterogeneous reaction of RHS with those model aerosols leads to different gaseous species like CO2, CO and small reactive/toxic molecules like phosgene (COCl2). Hydrogen containing groups on the aerosol particles are destroyed to form HCl or HBr, and a significant formation of C-Br bonds could be verified in the particle phase. Carbonyl containing functional groups of the aerosol are strongly affected by the halogenation process. While changes of functional groups and gaseous species were visible using FTIR spectroscopy, optical properties were studied using Diffuse Reflectance UV/VIS spectroscopy. Overall, the optical properties of the processed organic aerosols are significantly changed. While chlorine causes a "bleaching" of the aerosol particles, bromine shifts the maximum of UV/VIS absorption to the red end of the UV/VIS spectrum. Further physico-chemical changes were recognized according to the aerosol size-distributions or the

  11. Estimation of aerosol optical properties from all-sky imagers

    NASA Astrophysics Data System (ADS)

    Kazantzidis, Andreas; Tzoumanikas, Panagiotis; Salamalikis, Vasilios; Wilbert, Stefan; Prahl, Christoph

    2015-04-01

    Aerosols are one of the most important constituents in the atmosphere that affect the incoming solar radiation, either directly through absorbing and scattering processes or indirectly by changing the optical properties and lifetime of clouds. Under clear skies, aerosols become the dominant factor that affect the intensity of solar irradiance reaching the ground. It has been shown that the variability in direct normal irradiance (DNI) due to aerosols is more important than the one induced in global horizontal irradiance (GHI), while the uncertainty in its calculation is dominated by uncertainties in the aerosol optical properties. In recent years, all-sky imagers are used for the detection of cloud coverage, type and velocity in a bouquet of applications including solar irradiance resource and forecasting. However, information about the optical properties of aerosols could be derived with the same instrumentation. In this study, the aerosol optical properties are estimated with the synergetic use of all-sky images, complementary data from the Aerosol Robotic Network (AERONET) and calculations from a radiative transfer model. The area of interest is Plataforma Solar de Almería (PSA), Tabernas, Spain and data from a 5 month period are analyzed. The proposed methodology includes look-up-tables (LUTs) of diffuse sky radiance of Red (R), Green (G) and Blue (B) channels at several zenith and azimuth angles and for different atmospheric conditions (Angström α and β, single scattering albedo, precipitable water, solar zenith angle). Based on the LUTS, results from the CIMEL photometer at PSA were used to estimate the RGB radiances for the actual conditions at this site. The methodology is accompanied by a detailed evaluation of its robustness, the development and evaluation of the inversion algorithm (derive aerosol optical properties from RGB image values) and a sensitivity analysis about how the pre-mentioned atmospheric parameters affect the results.

  12. Dependence of Aerosol Light Absorption and Single-Scattering Albedo On Ambient Relative Humidity for Sulfate Aerosols with Black Carbon Cores

    NASA Technical Reports Server (NTRS)

    Redemann, Jens; Russell, Philip B.; Hamill, Patrick

    2001-01-01

    Atmospheric aerosols frequently contain hygroscopic sulfate species and black carbon (soot) inclusions. In this paper we report results of a modeling study to determine the change in aerosol absorption due to increases in ambient relative humidity (RH), for three common sulfate species, assuming that the soot mass fraction is present as a single concentric core within each particle. Because of the lack of detailed knowledge about various input parameters to models describing internally mixed aerosol particle optics, we focus on results that were aimed at determining the maximum effect that particle humidification may have on aerosol light absorption. In the wavelength range from 450 to 750 nm, maximum absorption humidification factors (ratio of wet to 'dry=30% RH' absorption) for single aerosol particles are found to be as large as 1.75 when the RH changes from 30 to 99.5%. Upon lesser humidification from 30 to 80% RH, absorption humidification for single particles is only as much as 1.2, even for the most favorable combination of initial ('dry') soot mass fraction and particle size. Integrated over monomodal lognormal particle size distributions, maximum absorption humidification factors range between 1.07 and 1.15 for humidification from 30 to 80% and between 1.1 and 1.35 for humidification from 30 to 95% RH for all species considered. The largest humidification factors at a wavelength of 450 nm are obtained for 'dry' particle size distributions that peak at a radius of 0.05 microns, while the absorption humidification factors at 700 nm are largest for 'dry' size distributions that are dominated by particles in the radius range of 0.06 to 0.08 microns. Single-scattering albedo estimates at ambient conditions are often based on absorption measurements at low RH (approx. 30%) and the assumption that aerosol absorption does not change upon humidification (i.e., absorption humidification equal to unity). Our modeling study suggests that this assumption alone can

  13. Remote Sensing of Spectral Aerosol Properties: A Classroom Experience

    NASA Technical Reports Server (NTRS)

    Levy, Robert C.; Pinker, Rachel T.

    2006-01-01

    Bridging the gap between current research and the classroom is a major challenge to today s instructor, especially in the sciences where progress happens quickly. NASA Goddard Space Flight Center and the University of Maryland teamed up in designing a graduate class project intended to provide a hands-on introduction to the physical basis for the retrieval of aerosol properties from state-of-the-art MODIS observations. Students learned to recognize spectral signatures of atmospheric aerosols and to perform spectral inversions. They became acquainted with the operational MODIS aerosol retrieval algorithm over oceans, and methods for its evaluation, including comparisons with groundbased AERONET sun-photometer data.

  14. Modelling the optical properties of aerosols in a chemical transport model

    NASA Astrophysics Data System (ADS)

    Andersson, E.; Kahnert, M.

    2015-12-01

    According to the IPCC fifth assessment report (2013), clouds and aerosols still contribute to the largest uncertainty when estimating and interpreting changes to the Earth's energy budget. Therefore, understanding the interaction between radiation and aerosols is both crucial for remote sensing observations and modelling the climate forcing arising from aerosols. Carbon particles are the largest contributor to the aerosol absorption of solar radiation, thereby enhancing the warming of the planet. Modelling the radiative properties of carbon particles is a hard task and involves many uncertainties arising from the difficulties of accounting for the morphologies and heterogeneous chemical composition of the particles. This study aims to compare two ways of modelling the optical properties of aerosols simulated by a chemical transport model. The first method models particle optical properties as homogeneous spheres and are externally mixed. This is a simple model that is particularly easy to use in data assimilation methods, since the optics model is linear. The second method involves a core-shell internal mixture of soot, where sulphate, nitrate, ammonia, organic carbon, sea salt, and water are contained in the shell. However, by contrast to previously used core-shell models, only part of the carbon is concentrated in the core, while the remaining part is homogeneously mixed with the shell. The chemical transport model (CTM) simulations are done regionally over Europe with the Multiple-scale Atmospheric Transport and CHemistry (MATCH) model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). The MATCH model was run with both an aerosol dynamics module, called SALSA, and with a regular "bulk" approach, i.e., a mass transport model without aerosol dynamics. Two events from 2007 are used in the analysis, one with high (22/12-2007) and one with low (22/6-2007) levels of elemental carbon (EC) over Europe. The results of the study help to assess the

  15. Diurnal Cycles of Aerosol Optical Properties at Pico Tres Padres, Mexico City: Evidences for Changes in Particle Morphology and Secondary Aerosol Formation

    NASA Astrophysics Data System (ADS)

    Mazzoleni, C.; Dubey, M.; Chakrabarty, R.; Moosmuller, H.; Onasch, T.; Zavala, M.; Herndon, S.; Kolb, C.

    2007-12-01

    Aerosol optical properties affect planetary radiative balance and depend on chemical composition, size distribution, and morphology. During the MILAGRO field campaign, we measured aerosol absorption and scattering in Mexico City using the Los Alamos aerosol photoacoustic (LAPA) instrument operating at 781 nm. The LAPA was mounted on-board the Aerodyne Research Inc. mobile laboratory, which hosted a variety of gaseous and aerosol instruments. During the campaign, the laboratory was moved to different sites, capturing spatial and temporal variability. Additionally, we collected ambient aerosols on Nuclepore filters for scanning electron microscopy (SEM) analysis. SEM images of selected filters were taken to study particle morphology. Between March 7th and 19th air was sampled at the top of Pico Tres Padres, a mountain on the north side of Mexico City. Aerosol absorption and scattering followed diurnal patterns related to boundary layer height and solar insulation. We report an analysis of aerosol absorption, scattering, and morphology for three days (9th, 11th and 12th of March 2006). The single scattering albedo (SSA, ratio of scattering to total extinction) showed a drop in the tens-of-minutes-to-hour time frame after the boundary layer grew above the sampling site. Later in the day the SSA rose steadily reaching a maximum in the afternoon. The SEM images showed a variety of aerosol shapes including fractal-like aggregates, spherical particles, and other shapes. The absorption correlated with the CO2 signal and qualitatively with the fraction of fractal-like particles to the total particle count. In the afternoon the SSA qualitatively correlated with a relative increase in spherical particles and total particle count. These observed changes in optical properties and morphology can be explained by the dominant contribution of freshly emitted particles in the morning and by secondary particle formation in the afternoon. SSA hourly averaged values ranged from ~0.63 in

  16. Aircraft observations of the physical and radiative properties of biomass aerosol particles during SAFARI-2000.

    NASA Astrophysics Data System (ADS)

    Osborne, S. R.; Haywood, J. M.

    2001-12-01

    An initial analysis will be shown from the ~80 h of data collected between 2--18 September 2000 by the UK Met Office C-130 aircraft during the dry season campaign of the Southern African Regional Science Initiative (SAFARI-2000). The talk will concentrate on the physical and optical properties of the biomass aerosol. The evolution of the particle size spectrum and its optical properties at emission and after ageing will be shown. The vertical distribution of the biomass plume over the land and sea will be compared in view of the local meteorology. A generalised three log-normal model is shown to represent aged biomass aerosol over the sea areas, both in terms of the number and mass particle size spectra, but also derived optical properties (e.g. asymmetry factor, single scatter albedo (ω 0) and extinction coefficient) as calculated using Mie theory and appropriate refractive indices. ω 0 was determined independently using a particle soot absorption photometer (giving the absorption coefficient at a wavelength of 0.567 μ m) and a nephelometer (giving the scattering coefficients at 0.45, 0.55 and 0.65 μ m). Good agreement was found between the measurements and those obtained from the Mie calculations and observed size distributions. A typical value of ω 0 at 0.55 μ m for aged biomass aerosol was 0.90. The radiative properties of the biomass aerosol over both land and sea will be summarised. Stratocumulus cloud was present on some of the days over the sea and the surprising lack of interaction between the elevated biomass plume (containing significant levels of cloud condensation nuclei) and the cloud capping the marine boundary layer will be illustrated. Using the cloud-free and cloudy case studies we can begin to elucidate the levels of direct and indirect forcing of the biomass aerosol on a regional scale. >http://www.mrfnet.demon.co.uk/africa/SAFARI2000.htm

  17. Decadal changes in aerosol absorption across Brazil resulting from changes in biomass burning practices

    NASA Astrophysics Data System (ADS)

    Coe, H.; Morgan, W.; Darbyshire, E.; Allan, J. D.; Flynn, M.; Liu, D.; Langridge, J.; Johnson, B. T.; Haywood, J. M.; Longo, K.; Artaxo, P.; Highwood, E.; Mollard, J.

    2015-12-01

    Open biomass burning makes a substantial contribution to the global budget of black carbon, yet models significantly underestimate absorption aerosol optical depth compared to observations by approximately a factor of two over South America. These large differences need to be addressed. Recent work has shown that the number of deforestation fires has decreased across Amazonia over the last decade, giving rise to a decrease in the abundance of biomass burning aerosol across the region. At the same time there has been an increase in the frequency of agricultural burning across regions that have previously been deforested, as well as increased burning in the east of Brazil in the Cerrado regions. We sampled both of these types of open burning extensively during a recent aircraft experiment. Significant concentrations of organic carbon as well as black carbon were observed, with this ratio providing the main control on the single scattering albedo (SSA).Deforestation fires and wild forest fires are prevalent across the south west of the Amazon Basin, where smouldering burning dominates. In the east of Brazil, agricultural burning proceeds via a much more efficient form of combustion and as a result, black carbon is a much larger fraction of the aerosol mass and SSAs are much lower than in the west. We have analysed MISR data across the region to show that whilst aerosol optical depths have decreased during the dry season over the last decade, with greater rates of reduction occurring over the south western margins of Amazonia, absorption aerosol optical depths have significantly increased over the Cerrado and remained constant over south western Amazonia. This has led to a decline in SSA across the whole of the region with greater reductions occurring over the eastern states. This finding is consistent with our aircraft measurements. We will discuss the implications of these changes for air quality and climate across the region.

  18. Aerosol particle properties in a South American megacity

    NASA Astrophysics Data System (ADS)

    Ulke, Ana; Torres-Brizuela, Marcela; Raga, Graciela; Baumgardner, Darrel; Cancelada, Marcela

    2015-04-01

    The subtropical city of Buenos Aires is located on the western shore of Río de la Plata, on the southeastern coast of Argentina. It is the second largest metropolitan area in South America, with a population density of around 14 thousand people per km2. When all 24 counties of the Great Buenos Aires Metropolitan Area are included it is the third-largest conurbation in Latin America, with a population of around fifteen million inhabitants. The generalized worldwide trend to concentrate human activities in urban regions that continue to expand in area, threatens the local and regional environment. Air pollution in the Buenos Aires airshed is due to local sources (mainly the mobile sources, followed by the electric power plants and some industries) and to distant sources (like biomass burning, dust, marine aerosols and occasionally volcanic ash) whose products arrive in the city area due to the regional transport patterns. Previous research suggests that ambient aerosol particle concentrations should be considered an air quality problem. A field campaign was conducted in Buenos Aires in 2011 in order to characterize some aerosol particles properties measured for the first time in the city. Measurements began in mid- April and continued until December. The field observations were done in a collaborative effort between the Universities of Mexico (UNAM) and Buenos Aires (UBA). A suite of instruments was installed on the roof of an UBA laboratory and classroom buildings (34.54° S, 58.44° W) at an altitude of approximately 30 m above sea level. The measurements included the number concentration of condensation nuclei (CN) larger than approximately 50 nm, the mass concentration of particle-bound polycyclic aromatic hydrocarbons (PPAH), the scattering (Bscat) and absorption (Babs) coefficients at 550 nm and the vertical profiles of backscattered light from aerosols at a wavelength of 910 nm using a ceilometer. In addition, a weather station recorded the meteorological

  19. Long-term Observation of Aerosol Optical Properties at the SORPES station in Nanjing, China

    NASA Astrophysics Data System (ADS)

    Shen, Yicheng; Ding, Aijun; Virkkula, Aki; Wang, Jiaping; Chi, Xuguang; Qi, Ximeng; Liu, Qiang; Zheng, Longfei; Xie, Yuning

    2016-04-01

    Atmospheric aerosols influence the earth's radiation budget by scattering and absorbing solar radiation and contribute substantial uncertainty in the estimation of climate forcing. Thorough and comprehensive measurements on different parameters including absorption and scattering coefficient, wavelength dependence and angular dependence along with their daily and seasonal variation help to understand the influence of aerosol on radiation. 2-years continuous measurement of aerosol optical properties has been conducted from June 2013 to May 2015 at the Station for Observing Regional Process of Earth System (SORPES) station, which is a regional background station located in downwind direction of Yangtze River Delta (YRD) urban agglomeration in China. A 7-wavelenths aethalometer and a 3-wavelenths nephelometer were used to measure absorption and scattering coefficient, and also other parameters like single scattering albedo (SSA), absorption angstrom Exponent (AAE), scattering angstrom exponent (SAE) and back-scattering refraction. In addtion, simultaneous measurements on chemical composition and particle size distribution were performed so as to investigate the dependencies of aerosol optical properties on chemical composition and size distribution. To get further insight on the influencing factors, Lagrangian particle dispersion modeling (LPDM) was employed for source identification in this study. The averages of absorption coefficient, scattering coefficient and SSA are 26.0±18.7 Mm-1, 426±327 Mm-1 , 0.936±0.3 at 520nm respectively for whole period. SAE between 450 and 635nm is 1.299±0.34 and have strong negative correlation with particle Surface Mean Diameter (SMD). AAE between 370 and 950nm is 1.043±0.15 for whole period but growth to more than 1.6 in all identified Biomass Burning (BB) events.

  20. Interpreting the ultraviolet aerosol index observed with the OMI satellite instrument to understand absorption by organic aerosols: implications for atmospheric oxidation and direct radiative effects

    NASA Astrophysics Data System (ADS)

    Hammer, Melanie S.; Martin, Randall V.; van Donkelaar, Aaron; Buchard, Virginie; Torres, Omar; Ridley, David A.; Spurr, Robert J. D.

    2016-03-01

    Satellite observations of the ultraviolet aerosol index (UVAI) are sensitive to absorption of solar radiation by aerosols; this absorption affects photolysis frequencies and radiative forcing. We develop a global simulation of the UVAI using the 3-D chemical transport model GEOS-Chem coupled with the Vector Linearized Discrete Ordinate Radiative Transfer model (VLIDORT). The simulation is applied to interpret UVAI observations from the Ozone Monitoring Instrument (OMI) for the year 2007. Simulated and observed values are highly consistent in regions where mineral dust dominates the UVAI, but a large negative bias (-0.32 to -0.97) exists between simulated and observed values in biomass burning regions. We determine effective optical properties for absorbing organic aerosol, known as brown carbon (BrC), and implement them into GEOS-Chem to better represent observed UVAI values over biomass burning regions. The inclusion of absorbing BrC decreases the mean bias between simulated and OMI UVAI values from -0.57 to -0.09 over West Africa in January, from -0.32 to +0.0002 over South Asia in April, from -0.97 to -0.22 over southern Africa in July, and from -0.50 to +0.33 over South America in September. The spectral dependence of absorption after including BrC in the model is broadly consistent with reported observations for biomass burning aerosol, with absorbing Ångström exponent (AAE) values ranging from 2.9 in the ultraviolet (UV) to 1.3 across the UV-Near IR spectrum. We assess the effect of the additional UV absorption by BrC on atmospheric photochemistry by examining tropospheric hydroxyl radical (OH) concentrations in GEOS-Chem. The inclusion of BrC decreases OH by up to 30 % over South America in September, up to 20 % over southern Africa in July, and up to 15 % over other biomass burning regions. Global annual mean OH concentrations in GEOS-Chem decrease due to the presence of absorbing BrC, increasing the methyl chloroform lifetime from 5.62 to 5.68 years

  1. Interpreting the Ultraviolet Aerosol Index observed with the OMI satellite instrument to understand absorption by organic aerosols: implications for atmospheric oxidation and direct radiative effects

    NASA Astrophysics Data System (ADS)

    Hammer, M. S.; Martin, R. V.; van Donkelaar, A.; Buchard, V.; Torres, O.; Ridley, D. A.; Spurr, R. J. D.

    2015-10-01

    Satellite observations of the Ultraviolet Aerosol Index (UVAI) are sensitive to absorption of solar radiation by aerosols; this absorption affects photolysis frequencies and radiative forcing. We develop a global simulation of the UVAI using the 3-D chemical transport model GEOS-Chem coupled with the Vector Linearized Discrete Ordinate Radiative Transfer model (VLIDORT). The simulation is applied to interpret UVAI observations from the Ozone Monitoring Instrument (OMI) for the year 2007. Simulated and observed values are highly consistent in regions where mineral dust dominates the UVAI, but a large negative bias (-0.32 to -0.97) exists between simulated and observed values in biomass burning regions. We determine effective optical properties for absorbing organic aerosol, known as brown carbon (BrC), and implement them into GEOS-Chem to better represent observed UVAI values over biomass burning regions. The addition of absorbing BrC decreases the mean bias between simulated and OMI UVAI values from -0.57 to -0.09 over West Africa in January, from -0.32 to +0.0002 over South Asia in April, from -0.97 to -0.22 over southern Africa in July, and from -0.50 to +0.33 over South America in September. The spectral dependence of absorption after adding BrC to the model is broadly consistent with reported observations for biomass burning aerosol, with Absorbing Angstrom Exponent (AAE) values ranging from 2.9 in the ultraviolet (UV) to 1.3 across the UV-Near IR spectrum. We assess the effect of the additional UV absorption by BrC on atmospheric photochemistry by examining tropospheric hydroxyl radical (OH) concentrations in GEOS-Chem. The inclusion of BrC decreases OH by up to 35 % over South America in September, up to 25 % over southern Africa in July, and up to 20 % over other biomass burning regions. Global annual mean OH concentrations in GEOS-Chem decrease due to the presence of absorbing BrC, increasing the methyl chloroform lifetime from 5.62 to 5.68 years, thus

  2. Interpreting the Ultraviolet Aerosol Index Observed with the OMI Satellite Instrument to Understand Absorption by Organic Aerosols: Implications for Atmospheric Oxidation and Direct Radiative Effects

    NASA Technical Reports Server (NTRS)

    Hammer, Melanie S.; Martin, Randall V.; Donkelaar, Aaron van; Buchard, Virginie; Torres, Omar; Ridley, David A.; Spurr, Robert J. D.

    2016-01-01

    Satellite observations of the ultraviolet aerosol index (UVAI) are sensitive to absorption of solar radiation by aerosols; this absorption affects photolysis frequencies and radiative forcing. We develop a global simulation of the UVAI using the 3-D chemical transport model GEOSChem coupled with the Vector Linearized Discrete Ordinate Radiative Transfer model (VLIDORT). The simulation is applied to interpret UVAI observations from the Ozone Monitoring Instrument (OMI) for the year 2007. Simulated and observed values are highly consistent in regions where mineral dust dominates the UVAI, but a large negative bias (-0.32 to -0.97) exists between simulated and observed values in biomass burning regions. We determine effective optical properties for absorbing organic aerosol, known as brown carbon (BrC), and implement them into GEOS-Chem to better represent observed UVAI values over biomass burning regions. The inclusion of absorbing BrC decreases the mean bias between simulated and OMI UVAI values from -0.57 to -0.09 over West Africa in January, from -0.32 to +0.0002 over South Asia in April, from -0.97 to -0.22 over southern Africa in July, and from -0.50 to +0.33 over South America in September. The spectral dependence of absorption after including BrC in the model is broadly consistent with reported observations for biomass burning aerosol, with absorbing Angstrom exponent (AAE) values ranging from 2.9 in the ultraviolet (UV) to 1.3 across the UV-Near IR spectrum. We assess the effect of the additional UV absorption by BrC on atmospheric photochemistry by examining tropospheric hydroxyl radical (OH) concentrations in GEOS-Chem. The inclusion of BrC decreases OH by up to 30% over South America in September, up to 20% over southern Africa in July, and up to 15% over other biomass burning regions. Global annual mean OH concentrations in GEOS-Chem decrease due to the presence of absorbing BrC, increasing the methyl chloroform lifetime from 5.62 to 5.68 years, thus

  3. The Measurement of Aerosol Optical Properties using Continuous Wave Cavity Ring-Down Techniques

    NASA Technical Reports Server (NTRS)

    Strawa, Anthony W.; Castaneda, Rene; Owano, Thomas; Baer, Douglas S.; Paldus, Barbara A.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    Large uncertainties in the effects that aerosols have on climate require improved in situ measurements of extinction coefficient and single-scattering albedo. This paper describes the use of continuous wave cavity ring-down (CW-CRD) technology to address this problem. The innovations in this instrument are the use of CW-CRD to measure aerosol extinction coefficient, the simultaneous measurement of scattering coefficient, and small size suitable for a wide range of aircraft applications. Our prototype instrument measures extinction and scattering coefficient at 690 nm and extinction coefficient at 1550 nm. The instrument itself is small (60 x 48 x 15 cm) and relatively insensitive to vibrations. The prototype instrument has been tested in our lab and used in the field. While improvements in performance are needed, the prototype has been shown to make accurate and sensitive measurements of extinction and scattering coefficients. Combining these two parameters, one can obtain the single-scattering albedo and absorption coefficient, both important aerosol properties. The use of two wavelengths also allows us to obtain a quantitative idea of the size of the aerosol through the Angstrom exponent. Minimum sensitivity of the prototype instrument is 1.5 x 10(exp -6)/m (1.5 M/m). Validation of the measurement of extinction coefficient has been accomplished by comparing the measurement of calibration spheres with Mie calculations. This instrument and its successors have potential to help reduce uncertainty currently associated with aerosol optical properties and their spatial and temporal variation. Possible applications include studies of visibility, climate forcing by aerosol, and the validation of aerosol retrieval schemes from satellite data.

  4. The Measurement of Aerosol Optical Properties Using Continuous Wave Cavity Ring-Down Techniques

    NASA Technical Reports Server (NTRS)

    Strawa, A. W.; Owano, T.; Castaneda, R.; Baer, D. S.; Paldus, B. A.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    Large uncertainties in the effects that aerosols have on climate require improved in-situ measurements of extinction coefficient and single-scattering albedo. This abstract describes the use of continuous wave cavity ring-down (CW-CRD) technology to address this problem. The innovations in this instrument are the use of CW-CRD to measure aerosol extinction coefficient, the simultaneous measurement of scattering coefficient, and small size suitable for a wide range of aircraft applications. Our prototype instrument measures extinction and scattering coefficient at 690 nm and extinction coefficient at 1550 nm. The instrument itself is small (60 x 48 x 15 cm) and relatively insensitive to vibrations. The prototype instrument has been tested in our lab and used in the field. While improvements in performance are needed, the prototype has been shown to make accurate and sensitive measurements of extinction and scattering coefficients. Combining these two parameters, one can obtain the single-scattering albedo and absorption coefficient, both important aerosol properties. The use of two wavelengths also allows us to obtain a quantitative idea of the size of the aerosol through the Angstrom exponent. Minimum sensitivity of the prototype instrument is 1.5 x 10(exp -6)/m (1.5/Mm). Validation of the measurement of extinction coefficient has been accomplished by comparing the measurement of calibration spheres with Mie calculations. This instrument and its successors have potential to help reduce uncertainty currently associated with aerosol optical properties and their spatial and temporal variation. Possible applications include studies of visibility, climate forcing by aerosol, and the validation of aerosol retrieval schemes from satellite data.

  5. Absorption, scattering and single scattering albedo of aerosols obtained from in situ measurements in the subarctic coastal region of Norway

    NASA Astrophysics Data System (ADS)

    Montilla, E.; Mogo, S.; Cachorro, V.; Lopez, J.; de Frutos, A.

    2011-01-01

    In situ measurements of aerosol optical properties were made in summer 2008 at the ALOMAR station facility (69°16 N, 16°00 E), located at a rural site in the North of the island of Andøya (Vesterålen archipelago), about 300 km north of the Arctic Circle. The extended three months campaign was part of the POLAR-CAT Project of the International Polar Year (IPY-2007-2008), and its goal was to characterize the aerosols of this sub-Arctic area which frequently transporte to the Arctic region. The ambient light-scattering coefficient, σs(550 nm), at ALOMAR had a hourly mean value of 5.412 Mm-1 (StD = 3.545 Mm-1) and the light-absorption coefficient, σa(550 nm), had an hourly mean value of 0.400 Mm-1 (StD = 0.273 Mm-1). The scattering/absorption Ångström exponents, αs,a, are used for detailed analysis of the variations of the spectral shape of σs,a. The single scattering albedo, &omega0, ranges from 0.622 to 0.985 (mean = 0.913, StD = 0.052) and the relation of this property to the absorption/scattering coefficients and the Ångström exponents is presented. The relationships between all the parameters analyzed, mainly those related to the single scattering albedo, allow us to describe the local atmosphere as extremely clean.

  6. Atmospheric Aging and Its Impacts on Physical Properties of Soot Aerosols: Results from the 2009 SHARP/SOOT Campaign

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Khalizov, A. F.; Zheng, J.; Reed, C. C.; Collins, D. R.; Olaguer, E. P.

    2009-12-01

    Atmospheric aerosols impact the Earth energy balance directly by scattering solar radiation back to space and indirectly by changing the albedo, frequency, and lifetime of clouds. Carbon soot (or black carbon) produced from incomplete combustion of fossil fuels and biomass burning represents a major component of primary aerosols. Because of high absorption cross-sections over a broad range of the electromagnetic spectra, black carbon contributes significantly to climate change by direct radiative forcing and is the second most important component causing global warming after carbon dioxide. In areas identified as aerosol hotspots, which include many megacities, solar heating by soot-containing aerosols is roughly comparable to heating due to greenhouse gases. In addition, light absorbing soot aerosols may reduce photolysis rates at the surface level, producing a noticeable impact on photochemistry. Enhanced light absorption and scattering by soot can stabilize the atmosphere, retarding vertical transport and exacerbating accumulation of gaseous and particulate matter (PM) pollutants within the planetary boundary layer. Less surface heating and atmospheric stabilization may decrease formation of clouds, and warming in the atmosphere can evaporate existing cloud droplets by lowering relative humidity. Furthermore, soot-containing aerosols represent a major type of PM that has adverse effects on human health. When first emitted, soot particles are low-density aggregates of loosely connected primary spherules. Freshly emitted soot particles are typically hydrophobic, but may become cloud condensation nuclei (CCN) during atmospheric aging by acquiring hydrophilic coatings. Hygroscopic soot particles, being efficient CCN, can exert indirect forcing on climate. In this talk, results will be presented on measurements of soot properties during the 2009 SHARP/SOOT Campaign. Ambient aerosols and fresh soot particles injected into a captured air chamber were monitored to

  7. Aerosol vertical distribution and optical properties over China from long-term satellite and ground-based remote sensing

    NASA Astrophysics Data System (ADS)

    Tian, Pengfei; Cao, Xianjie; Zhang, Lei; Sun, Naixiu; Sun, Lu; Logan, Timothy; Shi, Jinsen; Wang, Yuan; Ji, Yuemeng; Lin, Yun; Huang, Zhongwei; Zhou, Tian; Shi, Yingying; Zhang, Renyi

    2017-02-01

    than those of the less polluted regions, indicating a stabilized atmosphere due to absorptive aerosols in the polluted regions. Our results reveal that the satellite and ground-based remote-sensing measurements provide the key information on the long-term seasonal and spatial variations in the aerosol vertical distribution and optical properties, regional aerosol types, long-range transport and atmospheric stability, which can be utilized to more precisely assess the direct and indirect aerosol effects on weather and climate.

  8. Determination of the broadband optical properties of biomass burning aerosol

    NASA Astrophysics Data System (ADS)

    Bluvshtein, Nir; Flores, J. Michel; Segev, Lior; Lin, Peng; Laskin, Alexander; Rudich, Yinon

    2016-04-01

    The direct and semi-direct effects of atmospheric aerosol on the Earth's energy balance are still the two of the largest uncertainties in our understanding of anthropogenic radiative forcing. In this study we developed a new approach for determining high sensitivity broadband UV-Vis spectrum (300-650 nm) of extinction, scattering and absorption coefficients, single scattering albedo and the complex refractive index for continuous, spectral and time dependent, monitoring of polydisperse aerosols population. This new approach was applied in a study of biomass burning aerosol. Extinction, scattering and absorption coefficients (αext, αsca, αabs, respectively) were continually monitored using photoacoustic spectrometer coupled to a cavity ring down spectrometer (PA-CRD-AS) at 404 nm, a dual-channel Broadband cavity-enhanced spectrometer (BBCES) at 315-345 nm and 390-420 nm and a three channel integrating nephelometer (IN) centered at 457, 525 and 637 nm. During the biomass burning event, the measured aerosol number concentration increased by more than an order of magnitude relative to other week nights and the mode of the aerosols size distribution increased from 40-50 nm to 110nm diameter. αext and αsca increased by a factor of about 5.5 and 4.5, respectively. The αabs increased by a factor over 20, indicating a significant change in the aerosol overall chemical composition. The imaginary part of the complex RI at 404nm increased from its background level at about 0.02 to a peak of about 0.08 and the SSA decreased from 0.9 to about 0.6. Significant change of the absorption spectral dependence indicates formation of visible-light absorbing compounds. The mass absorption cross section of the water soluble organic aerosol (MACWSOA) reached up to about 12% of the corresponding value for black carbon (BC) at 450 nm and up to 30% at 300 nm. These results demonstrate the importance of biomass burning in understanding global and regional radiative forcing.

  9. In situ observations of aerosol physical and optical properties in northern India

    NASA Astrophysics Data System (ADS)

    Lihavainen, H.; Hyvarinen, A.; Hooda, R. K.; Raatikainen, T. E.; Sharma, V.; Komppula, M.

    2012-12-01

    The southern Asia, including India, is exposed to substantial quantities of particulate air pollution originating mainly from fossil fuel combustion and biomass burning. Besides serious adverse health effects, these aerosols cause a large reduction of solar radiation at the surface accompanied by a substantial atmospheric heating, which is expected to have significant influences on the air temperature, crop yields, livestock and water resources over the southern Asia. The various influences by aerosols in this region depend crucially on the development of aerosol emissions from household, industrial, transportation and biomass burning sectors. The main purpose of this study is to investigate several measured aerosol optical and physical properties. We take advantage of observations from two measurement stations which have been established by the Finnish Meteorological Institute and The Energy and Resources Institute. Another station is on the foothills of Himalayas, in Mukteshwar, about 350 km east of New Delhi at elevation about 2 km ASL. This site is considered as a rural background site. Measurements of aerosol size distribution (7-500 nm), PM10, PM2.5, aerosol scattering and absorption coefficients and weather parameters have been conducted since 2006. Another station is located at the outskirts of New Delhi, in Gual Pahari, about 35 km south of city centre. It is considered as an urban background site. Measurements of aerosol size distribution (7 nm- 10 μm), PM10, PM2.5, aerosol scattering and absorption coefficients, aerosol optical depth, aerosol vertical distribution (LIDAR), aerosol filter sampling for chemical characterization and weather parameters were conducted between 2008 and 2010. On the overall average PM10 and PM2.5 values were about 3-4 times higher in Gual Pahari than in Mukteshwar as expected, 216 and 126 μg m^-3, respectively. However, difference depended much on the season, so that during winter time PM10 and PM2.5 concentrations were about

  10. THERMAL PROPERTIES OF SECONDARY ORGANIC AEROSOLS

    EPA Science Inventory

    Volume concentrations of steady-state secondary organic aerosol (SOA) were measured in several hydrocarbon/NOx irradiation experiments. These measurements were used to estimate the thermal behavior of the particles that may be formed in the atmosphere. These laborator...

  11. Light-absorbing Aerosol Properties in the Kathmandu Valley during SusKat-ABC Field Campaign

    NASA Astrophysics Data System (ADS)

    Kim, S.; Yoon, S.; Kim, J.; Cho, C.; Jung, J.

    2013-12-01

    Light-absorbing aerosols, such as black carbon (BC), are major contributors to the atmospheric heating and the reduction of solar radiation reaching at the earth's surface. In this study, we investigate light-absorption and scattering properties of aerosols (i.e., BC mass concentration, aerosol solar-absorption/scattering efficiency) in the Kathmandu valley during Sustainable atmosphere for the Kathmandu valley (SusKat)-ABC campaign, from December 2012 to February 2013. Kathmandu City is among the most polluted cities in the world. However, there are only few past studies that provide basic understanding of air pollution in the Kathmandu Valley, which is not sufficient for designing effective mitigation measures (e.g., technological, financial, regulatory, legal and political measures, planning strategies). A distinct diurnal variation of BC mass concentration with two high peaks observed during wintertime dry monsoon period. BC mass concentration was found to be maximum around 09:00 and 20:00 local standard time (LST). Increased cars and cooking activities including substantial burning of wood and other biomass in the morning and in the evening contributed to high BC concentration. Low BC concentrations during the daytime can be explain by reduced vehicular movement and cooking activities. Also, the developmements of the boundary layer height and mountain-valley winds in the Kathmandu Valley paly a crucial role in the temproal variation of BC mass concentrations. Detailed radiative effects of light-absorbing aerosols will be presented.

  12. Aerosol Radiative Forcing Derived From SeaWIFS - Retrieved Aerosol Optical Properties

    NASA Technical Reports Server (NTRS)

    Chou, Mong-Dah; Chan, Pui-King; Wang, Menghua; Einaudi, Franco (Technical Monitor)

    2000-01-01

    To understand climatic implications of aerosols over global oceans, the aerosol optical properties retrieved from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) are analyzed, and the effects of the aerosols on the Earth's radiation budgets (aerosol radiative forcing, ARF) are computed using a radiative transfer model. It is found that the distribution of the SeaWiFS-retrieved aerosol optical thickness is distinctively zonal. The maximum in the equatorial region coincides with the Intertropical Convergence Zone, and the maximum in the Southern Hemispheric high latitudes coincides with the region of prevailing westerlies. The minimum aerosol optical thickness is found in the subtropical high pressure regions, especially in the Southern Hemisphere. These zonal patterns clearly demonstrate the influence of atmospheric circulation on the oceanic aerosol distribution. Over global oceans, aerosols reduce the annual mean net downward solar flux by 5.4 W m-2 at the top of the atmosphere and by 6.1 W m-2 at the surface. The largest ARF is found in the tropical Atlantic, Arabian Sea, Bay of Bengal, the coastal regions of Southeast and East Asia, and the Southern Hemispheric high latitudes. During the period of the Indonesian big fires (September-December 1997), the cooling due to aerosols is greater than 15 W m-2 at the top of the atmosphere and greater than 30 W m(exp -1) at the surface in the vicinity of the maritime continents. The atmosphere receives extra solar radiation by greater than 15 W m(exp -1) over a large area. These large changes in radiative fluxes are expected to have enhanced the atmospheric stability, weakened the atmospheric circulation, and augmented the drought condition during that period. It would be very instructive to simulate the regional climatic. The model-calculated clear sky solar flux at the top of the atmosphere is compared with that derived from the Clouds and the Earth's Radiant Energy System (CERES). The net downward solar flux of

  13. Measurements of the absorption and scattering coefficients of aerosol particles in suburb of Nanjing (China)

    NASA Astrophysics Data System (ADS)

    Yin, Yan; Chen, Yu; Wang, Weiwei; Yan, Jiade; Qian, Ling; Tong, Yaoqing; Lin, Zhenyi

    2008-08-01

    The absorption and scattering coefficients of atmospheric aerosols were continuously measured with a Photoacoustic Soot Spectrometer (PASS, DMT Inc. USA) at a suburb site of Nanjing, one of the regions experiencing rapid industrialization in China. The measurements were carried out during autumn and winter 2007. A preliminary analysis of the data shows that, the scattering coefficient, Bscat, is two to ten times larger than the absorption coefficient, Babs, implying that the aerosols formed/emitted in this area are more scattering than previous assumed, and can be more important in cooling the Earth-atmosphere system. The results also indicate that the absolute values of both parameters are very much dependent on the meteorological conditions, such as wind speed and direction, fog, rain, etc. as well as the time of the day. Higher values often appear at nighttimes when wind is weak, especially when a temperature inverse layer is present near the surface. Higher values of Bscat and Babs were also observed under hazy and foggy weather conditions or when wind is blown from east, where a large industrial zone is located. Simultaneous measurements of the number concentrations, chemical compositions, and size distributions of aerosol particles are used to explain the characteristics of the changes in Bscat and Babs.

  14. Total ozone and aerosol optical depths inferred from radiometric measurements in the Chappuis absorption band

    SciTech Connect

    Flittner, D.E.; Herman, B.M.; Thome, K.J.; Simpson, J.M.; Reagan, J.A. )

    1993-04-15

    A second-derivative smoothing technique, commonly used in inversion work, is applied to the problem of inferring total columnar ozone amounts and aerosol optical depths. The application is unique in that the unknowns (i.e., total columnar ozone and aerosol optical depth) may be solved for directly without employing standard inversion methods. It is shown, however, that by employing inversion constraints, better solutions are normally obtained. The current method requires radiometric measurements of total optical depth through the Chappuis ozone band. It assumes no a priori shape for the aerosol optical depth versus wavelength profile and makes no assumptions about the ozone amount. Thus, the method is quite versatile and able to deal with varying total ozone and various aerosol size distributions. The technique is applied first in simulation, then to 119 days of measurements taken in Tucson, Arizona, that are compared to TOMS values for the same dates. The technique is also applied to two measurements taken at Mauna Loa, Hawaii, for which Dobson ozone values are available in addition to the TOMS values, and the results agree to within 15%. It is also shown through simulations that additional information can be obtained from measurements outside the Chappuis band. This approach reduces the bias and spread of the estimates total ozone and is unique in that it uses measurements from both the Chappuis and Huggins absorption bands. 12 refs., 6 figs., 2 tabs.

  15. International Workshop on Stratospheric Aerosols: Measurements, Properties, and Effects

    NASA Technical Reports Server (NTRS)

    Pueschel, Rudolf F. (Editor)

    1991-01-01

    Following a mandate by the International Aerosol Climatology Program under the auspices of International Association of Meteorology and Atmospheric Physics International Radiation Commission, 45 scientists from five nations convened to discuss relevant issues associated with the measurement, properties, and effects of stratospheric aerosols. A summary is presented of the discussions on formation and evolution, transport and fate, effects on climate, role in heterogeneous chemistry, and validation of lidar and satellite remote sensing of stratospheric aerosols. Measurements are recommended of the natural (background) and the volcanically enhanced aerosol (sulfuric acid and silica particles), the exhaust of shuttle, civil aviation and supersonic aircraft operations (alumina, soot, and ice particles), and polar stratospheric clouds (ice, condensed nitric and hydrochloric acids).

  16. Aerosol Properties and Radiative Forcing over Kanpur during Severe Aerosol Loading Conditions

    SciTech Connect

    Kaskaoutis, D. G.; Sinha, P. R.; Vinoj, V.; Kosmopoulos, P. G.; Tripathi, S. N.; Misra, Amit; Sharma, M.; Singh, R. P.

    2013-11-01

    Atmospheric aerosols over India exhibit large spatio-temporal fluctuation driven by the local monsoon system, emission rates and seasonally-changed air masses. The northern part of India is well-known for its high aerosol loading throughout the year due to anthropogenic emissions, dust influence and biomass burning. On certain circumstances and, under favorable weather conditions, the aerosol load can be severe, causing significant health concerns and climate implications. The present work analyzes the aerosol episode (AE) days and examines the modification in aerosol properties and radiative forcing during the period 2001-2010 based on Kanpur-AERONET sun photometer data. As AEs are considered the days having daily-mean aerosol optical depth (AOD) above the decadal mean + 1 STD (standard deviation); the threshold value is defined at 0.928. The results identify 277 out of 2095 days (13.2%) of AEs over Kanpur, which are most frequently observed during post-monsoon (78 cases, 18.6%) and monsoon (76, 14.7%) seasons due to biomass-burning episodes and dust influence, respectively. On the other hand, the AEs in winter and pre-monsoon are lower in both absolute and percentage values (65, 12.5% and 58, 9.1%, respectively). The modification in aerosol properties on the AE days is strongly related to season. Thus, in post-monsoon and winter the AEs are associated with enhanced presence of fine-mode aerosols and Black Carbon from anthropogenic pollution and any kind of burning, while in pre-monsoon and monsoon seasons they are mostly associated with transported dust. Aerosol radiative forcing (ARF) calculated using SBDART shows much more surface (~-69 to -97 Wm-2) and Top of Atmosphere cooling (-20 to -30 Wm-2) as well as atmospheric heating (~43 to 71 Wm-2) during the AE days compared to seasonal means. These forcing values are mainly controlled by the higher AODs and the modified aerosol characteristics (Angstrom α, SSA) during the AE days in each season and may cause

  17. Linking aerosol size and optical properties to trace gases emitted from biomass burning in real-time

    NASA Astrophysics Data System (ADS)

    McMeeking, G. R.; Carrico, C. M.; Stockwell, C.; Yokelson, R. J.; Veres, P. R.; DeMott, P. J.; Kreidenweis, S. M.

    2014-12-01

    Biomass burning aerosols have large impacts on regional and global climate that are partly determined by their optical properties. The optical properties of aerosol depend on their size and composition, which in turn are related to fire combustion processes. Here we investigate relationships between a large suite of trace gases and aerosol size and optical properties to better understand processes governing the optical properties of fresh biomass burning aerosol emissions. We examined over 100 individual burns of biomass fuels during the Fire Laboratory at Missoula Experiment 4 (FLAME 4). Emissions were measured directly from an exhaust stack designed to capture all emissions from relatively small-scale fires burned at the base of a large burn chamber. Trace gas species were measured using a combination of an open-path Fourier transform infrared spectrometer (OP-FTIR) and proton-transfer mass spectrometer (PTR-MS). Aerosol optical properties at 870 nm were measured using a photoacoustic extinctiometer (PAX) and particle size distributions were measured using a Fast Mobility Particle Sizer (FMPS) and Aerodynamic Particle Sizer. The rapid response of the instruments allowed for comparisons of the emissions and particle properties over the duration of the fire. For example, we observed correlations between aerosol absorption, particle size, and gas-phase species associated with different types of combustion such as flaming and smoldering. We also report fire-integrated emissions for aerosol absorption and scattering coefficients and compare these to other fire-integrated properties. Many of our burn experiments examined a number of fuels that had not before been characterized in laboratory conditions, including a number of peat fuels, African savanna grasses and crop residuals.

  18. Optical Properties of Polymers Relevant to Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Marrero-Ortiz, W.; Gomez-Hernandez, M. E.; Xu, W.; Guo, S.; Zhang, R.

    2014-12-01

    Atmospheric aerosols play a critical role in climate directly by scattering and absorbing solar radiation and indirectly by modifying the cloud formation. Currently, the direct and indirect effects of aerosols represent the largest uncertainty in climate predictions models. Some aerosols are directly emitted, but the majority are formed in the atmosphere by the oxidation of gaseous precursors. However, the formation of aerosols at the molecular level is not fully characterized. Certain category of secondary organic aerosols (SOA), which represent a significant fraction of the total aerosol burden, can be light-absorbing, also known as brown carbon. However, the overall contribution of SOA to the brown carbon and the related climate forcing is poorly understood. Such incomplete understanding is due in part to the chemical complexity of SOA and the lack of knowledge regarding SOA formation, transformation, and optical properties. Based on previous laboratory experiments, field measurements, and modeling studies, it has been suggested that the polymers and oligomers play an important role in the SOA formation. Atmospheric polymers could be produced by the hydration or heterogeneous reactions of epoxides and small α-dicarbonyls. Their aqueous chemistry products have been shown to give light-absorbing and high molecular weight oligomeric species, which increase the SOA mass production and alter the direct and indirect effect of aerosols. In this paper, the aerosol chemistry of small α-dicarbonyl compounds with amines is investigated and the associated optical properties are measured using spectroscopic techniques. The differences between primary, secondary and tertiary amines with glyoxal and methylglyoxal are evaluated in terms of SOA browning efficiency. Atmospheric implications of our present work for understanding the formation of light-absorbing SOA will be presented, particularly in terms of the product distribution of light-absorbing SOA formed by aqueous phase

  19. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    DOE PAGES

    Pistone, Kristina; Praveen, Puppala S.; Thomas, Rick M.; ...

    2016-04-27

    There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric vertical structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season.In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements were made of atmospheric precipitable water vapor (PWV)more » and the liquid water path (LWP) of trade cumulus clouds, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol from instrumentation at a ground observatory and on small unmanned aircraft. We present observations which indicate a positive correlation between aerosol and cloud LWP only when considering cases with low atmospheric water vapor (PWV < 40 kg m–2), a criterion which acts to filter the data to control for the natural meteorological variability in the region.We then use the aircraft and ground-based measurements to explore possible mechanisms behind this observed aerosol–LWP correlation. The increase in cloud liquid water is found to coincide with a lowering of the cloud base, which is itself attributable to increased boundary layer humidity in polluted conditions. High pollution is found to correlate with both higher temperatures and higher humidity measured throughout the boundary layer. A large-scale analysis, using satellite observations and meteorological reanalysis, corroborates these covariations: high-pollution cases are shown to originate as a highly polluted boundary layer air mass approaching the observatory from a

  20. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    SciTech Connect

    Pistone, Kristina; Praveen, Puppala S.; Thomas, Rick M.; Ramanathan, Veerabhadran; Wilcox, Eric M.; Bender, Frida A.-M.

    2016-04-27

    There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric vertical structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season.

    In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements were made of atmospheric precipitable water vapor (PWV) and the liquid water path (LWP) of trade cumulus clouds, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol from instrumentation at a ground observatory and on small unmanned aircraft. We present observations which indicate a positive correlation between aerosol and cloud LWP only when considering cases with low atmospheric water vapor (PWV < 40 kg m–2), a criterion which acts to filter the data to control for the natural meteorological variability in the region.

    We then use the aircraft and ground-based measurements to explore possible mechanisms behind this observed aerosol–LWP correlation. The increase in cloud liquid water is found to coincide with a lowering of the cloud base, which is itself attributable to increased boundary layer humidity in polluted conditions. High pollution is found to correlate with both higher temperatures and higher humidity measured throughout the boundary layer. A large-scale analysis, using satellite observations and meteorological reanalysis, corroborates these covariations: high-pollution cases are shown to originate as a highly polluted boundary layer air mass approaching the

  1. Reduction in biomass burning aerosol light absorption upon humidification: roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer

    NASA Astrophysics Data System (ADS)

    Lewis, K. A.; Arnott, W. P.; Moosmüller, H.; Chakrabarty, R. K.; Carrico, C. M.; Kreidenweis, S. M.; Day, D. E.; Malm, W. C.; Laskin, A.; Jimenez, J. L.; Ulbrich, I. M.; Huffman, J. A.; Onasch, T. B.; Trimborn, A.; Liu, L.; Mishchenko, M. I.

    2009-11-01

    Smoke particle emissions from the combustion of biomass fuels typical for the western and southeastern United States were studied and compared under high humidity and ambient conditions in the laboratory. The fuels used were Montana ponderosa pine (Pinus ponderosa), southern California chamise (Adenostoma fasciculatum), and Florida saw palmetto (Serenoa repens). Information on the non-refractory chemical composition of biomass burning aerosol from each fuel was obtained with an aerosol mass spectrometer and through estimation of the black carbon concentration from light absorption measurements at 870 nm. Changes in the optical and physical particle properties under high humidity conditions were observed for hygroscopic smoke particles containing substantial inorganic mass fractions that were emitted from combustion of chamise and palmetto fuels. Light scattering cross sections increased under high humidity for these particles, consistent with the hygroscopic growth measured for 100 nm particles in HTDMA measurements. Photoacoustic measurements of aerosol light absorption coefficients revealed a 20% reduction with increasing relative humidity, contrary to the expectation of light absorption enhancement by the liquid coating taken up by hygroscopic particles. This reduction is hypothesized to arise from two mechanisms: (1) shielding of inner monomers after particle consolidation or collapse with water uptake; (2) the lower case contribution of mass transfer through evaporation and condensation at high relative humidity (RH) to the usual heat transfer pathway for energy release by laser-heated particles in the photoacoustic measurement of aerosol light absorption. The mass transfer contribution is used to evaluate the fraction of aerosol surface covered with liquid water solution as a function of RH.

  2. Reduction in biomass burning aerosol light absorption upon humidification: roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer

    NASA Astrophysics Data System (ADS)

    Lewis, K. A.; Arnott, W. P.; Moosmüller, H.; Chakrabarty, R. K.; Carrico, C. M.; Kreidenweis, S. M.; Day, D. E.; Malm, W. C.; Laskin, A.; Jimenez, J. L.; Ulbrich, I. M.; Huffman, J. A.; Onasch, T. B.; Trimborn, A.; Liu, L.; Mishchenko, M. I.

    2009-07-01

    Smoke particle emissions from the combustion of biomass fuels typical for the western and southeastern United States were studied and compared under high humidity and ambient conditions in the laboratory. The fuels used are Montana ponderosa pine (Pinus ponderosa), southern California chamise (Adenostoma fasciculatum), and Florida saw palmetto (Serenoa repens). Information on the non-refractory chemical composition of biomass burning aerosol from each fuel was obtained with an aerosol mass spectrometer and through estimation of the black carbon concentration from light absorption measurements at 870 nm. Changes in the optical and physical particle properties under high humidity conditions were observed for hygroscopic smoke particles containing substantial inorganic mass fractions that were emitted from combustion of chamise and palmetto fuels. Light scattering cross sections increased under high humidity for these particles, consistent with the hygroscopic growth measured for 100 nm particles in HTDMA measurements. Photoacoustic measurements of aerosol light absorption coefficients reveal a 20% reduction with increasing relative humidity, contrary to the expectation of light absorption enhancement by the liquid coating taken up by hygroscopic particles. This reduction is hypothesized to arise from two mechanisms: 1. Shielding of inner monomers after particle consolidation or collapse with water uptake; 2. The contribution of mass transfer through evaporation and condensation at high relative humidity to the usual heat transfer pathway for energy release by laser-heated particles in the photoacoustic measurement of aerosol light absorption. The mass transfer contribution is used to evaluate the fraction of aerosol surface covered with liquid water solution as a function of RH.

  3. Aerosol Properties over the Eastern North Pacific based on Measurements from the MAGIC Field Campaign

    NASA Astrophysics Data System (ADS)

    Lewis, E. R.; Senum, G.; Springston, S. R.; Kuang, C.

    2015-12-01

    The MAGIC field campaign, funded and operated by the ARM (Atmospheric Radiation Measurement) Climate Research Facility of the US Department of Energy, occurred between September 2012 and October, 2013 aboard the Horizon Lines cargo container ship Spirit making regular trips between Los Angeles, CA and Honolulu, HI. Along this route, which lies very near the GPCI (GCSS Pacific Cross-section Intercomparison) transect, the predominant cloud regime changes from stratocumulus near the California coast to trade-wind cumulus near Hawaii. The transition between these two regimes is poorly understood and not accurately represented in models. The goal of MAGIC was to acquire statistic of this transition and thus improve its representation in models by making repeated transects through this region and measuring properties of clouds and precipitation, aerosols, radiation, and atmospheric structure. To achieve these goals, the Second ARM Mobile Facility (AMF2) was deployed on the Horizon Spirit as it ran its regular route between Los Angeles and Honolulu. AMF2 consists of three 20-foot SeaTainers and includes three radars and other instruments to measure properties of clouds and precipitation; the Aerosol Observing System (AOS), which has a suite of instruments to measure properties of aerosols; and other instruments to measure radiation, meteorological quantities, and sea surface temperature. Two technicians accompanied the AMF2, and scientists rode the ship as observers. MAGIC made nearly 20 round trips between Los Angeles and Honolulu (and thus nearly 40 excursions through the stratocumulus-to-cumulus transition) and spent 200 days at sea, collecting an unprecedented data set. Aerosol properties measured with the AOS include number concentration and size distribution, CCN activity, hygroscopic growth, and light-scattering and absorption. Additionally, more than one hundred filter samples were collected. Aerosol properties and their spatial and temporal behavior are discussed

  4. Retrieval of aerosol optical properties over land using PMAp

    NASA Astrophysics Data System (ADS)

    Grzegorski, Michael; Munro, Rosemary; Lang, Ruediger; Poli, Gabriele; Holdak, Andriy

    2015-04-01

    The retrieval of aerosol optical properties is an important task for industry and climate forecasting. An ideal instrument should include observations with moderate spectral and high spatial resolutions for a wide range of wavelengths (from the UV to the TIR), measurements of the polarization state at different wavelengths and measurements of the same scene for different observation geometries. As such an ideal instrument is currently unavailable the usage of different instruments on one satellite platform is an alternative choice. Since February 2014, the Polar Multi sensor Aerosol product (PMAp) is delivered as operational GOME product to our customers. The algorithms retrieve aerosol optical properties over ocean (AOD, volcanic ash, aerosol type) using a multi-sensor approach (GOME, AVHRR, IASI). The next releases of PMAp will provide an extended set of aerosol and cloud properties which include AOD over land and an improved volcanic ash retrieval combining AVHRR and IASI. This presentation gives an overview on the existing product and the prototypes in development. The major focus is the discussion of the AOD retrieval over land implemented in the upcoming PMAp2 release. In addition, the results of our current validation studies (e.g. comparisons to AERONET, other satellite platforms and model data) are shown.

  5. Optical and Physicochemical Properties of Brown Carbon Aerosol: Light Scattering, FTIR Extinction Spectroscopy, and Hygroscopic Growth.

    PubMed

    Tang, Mingjin; Alexander, Jennifer M; Kwon, Deokhyeon; Estillore, Armando D; Laskina, Olga; Young, Mark A; Kleiber, Paul D; Grassian, Vicki H

    2016-06-23

    A great deal of attention has been paid to brown carbon aerosol in the troposphere because it can both scatter and absorb solar radiation, thus affecting the Earth's climate. However, knowledge of the optical and chemical properties of brown carbon aerosol is still limited. In this study, we have investigated different aspects of the optical properties of brown carbon aerosol that have not been previously explored. These properties include extinction spectroscopy in the mid-infrared region and light scattering at two different visible wavelengths, 532 and 402 nm. A proxy for atmospheric brown carbon aerosol was formed from the aqueous reaction of ammonium sulfate with methylglyoxal. The different optical properties were measured as a function of reaction time for a period of up to 19 days. UV/vis absorption experiments of bulk solutions showed that the optical absorption of aqueous brown carbon solution significantly increases as a function of reaction time in the spectral range from 200 to 700 nm. The analysis of the light scattering data, however, showed no significant differences between ammonium sulfate and brown carbon aerosol particles in the measured scattering phase functions, linear polarization profiles, or the derived real parts of the refractive indices at either 532 or 402 nm, even for the longest reaction times with greatest visible extinction. The light scattering experiments are relatively insensitive to the imaginary part of the refractive index, and it was only possible to place an upper limit of k ≤ 0.01 on the imaginary index values. These results suggest that after the reaction with methylglyoxal the single scattering albedo of ammonium sulfate aerosol is significantly reduced but that the light scattering properties including the scattering asymmetry parameter, which is a measure of the relative amount of forward-to-backward scattering, remain essentially unchanged from that of unprocessed ammonium sulfate. The optical extinction properties

  6. Uncertainties of simulated aerosol optical properties induced by assumptions on aerosol physical and chemical properties: An AQMEII-2 perspective

    NASA Astrophysics Data System (ADS)

    Curci, G.; Hogrefe, C.; Bianconi, R.; Im, U.; Balzarini, A.; Baró, R.; Brunner, D.; Forkel, R.; Giordano, L.; Hirtl, M.; Honzak, L.; Jiménez-Guerrero, P.; Knote, C.; Langer, M.; Makar, P. A.; Pirovano, G.; Pérez, J. L.; San José, R.; Syrakov, D.; Tuccella, P.; Werhahn, J.; Wolke, R.; Žabkar, R.; Zhang, J.; Galmarini, S.

    2015-08-01

    The calculation of aerosol optical properties from aerosol mass is a process subject to uncertainty related to necessary assumptions on the treatment of the chemical species mixing state, density, refractive index, and hygroscopic growth. In the framework of the AQMEII-2 model intercomparison, we used the bulk mass profiles of aerosol chemical species sampled over the locations of AERONET stations across Europe and North America to calculate the aerosol optical properties under a range of common assumptions for all models. Several simulations with parameters perturbed within a range of observed values are carried out for July 2010 and compared in order to infer the assumptions that have the largest impact on the calculated aerosol optical properties. We calculate that the most important factor of uncertainty is the assumption about the mixing state, for which we estimate an uncertainty of 30-35% on the simulated aerosol optical depth (AOD) and single scattering albedo (SSA). The choice of the core composition in the core-shell representation is of minor importance for calculation of AOD, while it is critical for the SSA. The uncertainty introduced by the choice of mixing state choice on the calculation of the asymmetry parameter is the order of 10%. Other factors of uncertainty tested here have a maximum average impact of 10% each on calculated AOD, and an impact of a few percent on SSA and g. It is thus recommended to focus further research on a more accurate representation of the aerosol mixing state in models, in order to have a less uncertain simulation of the related optical properties.

  7. Aerosol absorption over Bay of Bengal during winter: Variability and sources

    NASA Astrophysics Data System (ADS)

    Kedia, Sumita; Ramachandran, S.; Rajesh, T. A.; Srivastava, Rohit

    2012-07-01

    Measurements of black carbon (BC) mass concentration were made over the Bay of Bengal (BoB) during the period of 27 December 2008-29 January 2009. BC mass concentration is highest over the Coastal-BoB (5.1 ± 3.0 μg m-3) and is more than a factor of two higher than the South-BoB (2.5 ± 1.4 μg m-3). The source regions of BC over the study region is identified using the Total Potential Source Contribution Function (TPSCF) analysis. The probable source regions over the Coastal-BoB and North-BoB (India, Indo-Gangetic plain, Pakistan, Afghanistan) are found to be distinctly different than that over the East-BoB and South-BoB (mostly from southeast Asia). The spectral distribution of absorption coefficients suggested similar source types of BC present over the entire BoB, with significant contribution of absorbing aerosols from the sources other than fossil fuel burning. Our results suggest that the entire BoB remains dominantly influenced by aerosols emitted from biomass/biofuel burning during winter. Single scattering albedo (SSA) is found to vary in the range of 0.63-0.70 over different parts of BoB with the lowest value over Coastal-BoB and the highest value over South-BoB. SSA values observed in the present study are the lowest ever reported over the BoB in the last decade indicating highest concentration of absorbing aerosols over the BoB during winter. The present work and the results obtained will have strong implications while investigating the effect of anthropogenic aerosols over marine environment, and in estimating the spatiotemporal variation of aerosol radiative impact.

  8. Evolution of biomass burning aerosol over the Amazon: airborne measurements of aerosol chemical composition, microphysical properties, mixing state and optical properties during SAMBBA

    NASA Astrophysics Data System (ADS)

    Morgan, W.; Allan, J. D.; Flynn, M.; Darbyshire, E.; Hodgson, A.; Liu, D.; O'Shea, S.; Bauguitte, S.; Szpek, K.; Johnson, B.; Haywood, J.; Longo, K.; Artaxo, P.; Coe, H.

    2013-12-01

    Biomass burning represents one of the largest sources of particulate matter to the atmosphere, resulting in a significant perturbation to the Earth's radiative balance coupled with serious impacts on public health. On regional scales, the impacts are substantial, particularly in areas such as the Amazon Basin where large, intense and frequent burning occurs on an annual basis for several months. Absorption by atmospheric aerosols is underestimated by models over South America, which points to significant uncertainties relating to Black Carbon (BC) aerosol properties. Initial results from the South American Biomass Burning Analysis (SAMBBA) field experiment, which took place during September and October 2012 over Brazil on-board the UK Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft, are presented here. Aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) and a DMT Single Particle Soot Photometer (SP2). The physical, chemical and optical properties of the aerosols across the region will be characterized in order to establish the impact of biomass burning on regional air quality, weather and climate. The aircraft sampled a range of conditions including sampling of pristine Rainforest, fresh biomass burning plumes, regional haze and elevated biomass burning layers within the free troposphere. The aircraft sampled biomass burning aerosol across the southern Amazon in the states of Rondonia and Mato Grosso, as well as in a Cerrado (Savannah-like) region in Tocantins state. This presented a range of fire conditions, in terms of their number, intensity, vegetation-type and their combustion efficiencies. Near-source sampling of fires in Rainforest environments suggested that smouldering combustion dominated, while flaming combustion dominated in the Cerrado. This led to significant differences in aerosol chemical composition, particularly in terms of the BC content, with BC being enhanced in the Cerrado

  9. Effect of CALIPSO Cloud Aerosol Discrimination (CAD) Confidence Levels on Observations of Aerosol Properties near Clouds

    NASA Technical Reports Server (NTRS)

    Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Liu, Zhaoyan

    2012-01-01

    CALIPSO aerosol backscatter enhancement in the transition zone between clouds and clear sky areas is revisited with particular attention to effects of data selection based on the confidence level of cloud-aerosol discrimination (CAD). The results show that backscatter behavior in the transition zone strongly depends on the CAD confidence level. Higher confidence level data has a flatter backscatter far away from clouds and a much sharper increase near clouds (within 4 km), thus a smaller transition zone. For high confidence level data it is shown that the overall backscatter enhancement is more pronounced for small clear-air segments and horizontally larger clouds. The results suggest that data selection based on CAD reduces the possible effects of cloud contamination when studying aerosol properties in the vicinity of clouds.

  10. Light Absorption of Black Carbon Aerosol and Its Radiative Forcing Effect in an Megacity Atmosphere in South China

    NASA Astrophysics Data System (ADS)

    Lan, Zijuan

    2013-04-01

    The effects of black carbon (BC) aerosol on climate warming have been the study focus in the recent decade, the regional effect of BC light absorption is more significant. The reduction of BC is now expected to have significant near-term climate change mitigation. Mass absorption efficient (MAE) was one of the important optical properties of BC aerosol for evaluating the BC on its radiative forcing effect, while BC mixing state is one main influencing factor for MAE. Models have estimated that BC radiative forcing can be increased by a factor of ~2 for internally versus externally mixed BC. On the other hand, some organic carbon had been found to significantly absorb light at UV or shorter wavelengths in the most recent studies, with strong spectral dependence. But large uncertainties still remain in determining the positive forcing effect of BC on global clime change due to the technical limitations. In this study, advanced instrumentation (a three-wavelength photoacoustic soot spectrometer (PASS-3) and a single particle soot photometer (SP2)) were used to measure black carbon aerosol and analyze its optical properties in a megacity in South China, Shenzhen, during the summer of 2011. It is in the southeast corner of the Pearl River Delta (PRD) region, neighboring Hong Kong to the south. During the campaign, the average BC mass concentration was 4.0±3.1 μg m-3, accounting for about 11% of PM2.5 mass concentration, which mainly came from fossil fuel combustion rather than biomass burning. The MAE of BC ranged from 5.0 to 8.5 m2 g-1, with an average value of 6.5±0.5 m2 g-1. The percentage of internally mixed BC was averagely 24.3±7.9% and positively correlated with the MAE. It is estimated that the internally mixed BC amplified MAE by about 7% during the campaign, suggesting that the BC absorption enhancement due to internal mixing in the real atmosphere is relatively low in comparison with the predictions by theoretical models, which stands in accordance with

  11. MAX-DOAS measurements in southern China: 1. automated aerosol profile retrieval using oxygen dimers absorptions

    NASA Astrophysics Data System (ADS)

    Li, X.; Brauers, T.; Shao, M.; Garland, R. M.; Wagner, T.; Deutschmann, T.; Wahner, A.

    2008-09-01

    We performed MAX-DOAS measurements during the PRiDe-PRD2006 campaign in the Pearl River Delta region 50 km north of Guangzhou, China, for 4 weeks in June 2006. We used an instrument which simultaneously sampled the wavelength range from 292 nm to 443 nm at 7 different elevation angles between 3° and 90°. Here we show that the O4 (O2 dimer) absorption at 360 nm can be used to retrieve the aerosol extinction and the height of the boundary layer. A comparison with simultaneously recorded, ground based nephelometer data shows an excellent agreement.

  12. Background Maritime Aerosol: Their Optical Thickness and Scattering Properties

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Smirnov, Alexander; Holben, Brent N.; Dubovik, Oleg; Einaudi, Franco (Technical Monitor)

    2001-01-01

    The effect of human induced change in the aerosol concentration and properties, or the aerosol response to climate change (e.g. droughts producing fires or dust) should be measured relative to a "background aerosol". How to define this background aerosol, so that it is both measurable and useful? Here we use 10 stations located in the Pacific, Atlantic and Indian Oceans to answer this question. Using a data set of the spectral optical thickness measured by the Aerosol Robotic network (AERONET), extending 1-3 years, we find the background conditions for these stations. The oceanic background aerosol is the result of ocean emission and spray, and some residual long lived continental aerosol. Its source is very broadly spread and is expected to vary little in time. Pollution or dust sources are from specific locations, emitted and transported to the measuring site in specific combination of meteorological conditions. Therefore they are expected to vary with time. It follows that the background aerosol can be identified as the median for conditions with small variations. To define the background we compute the median of N consequent measurements. We use N=50 that in average cloudy conditions corresponds to 2-3 days of measurements and N=100 (4-5 days). Most high polluted or dusty conditions correspond to data sequences with high standard deviation (greater than 0.02 in optical thickness) and are excluded. From the remaining N point running medians with low standard deviations we derive again the median. This excludes those rare cases of pollution or dust that is stable during the N measurements. The results show that the background aerosol over the Pacific Ocean is characterize by optical thickness of 0.055 at 500 nm and Angstrom exponent of 0.74. Over the Atlantic Ocean the values are 0.070 and 1.1 respectively, with little influence of the assumed value of N (50 or 100). The derivation of the background uses 20,000 and 5000 medians respectively that passed the

  13. Composition and physical properties of the Asian Tropopause Aerosol Layer and the North American Tropospheric Aerosol Layer

    PubMed Central

    Yu, Pengfei; Toon, Owen B; Neely, Ryan R; Martinsson, Bengt G; Brenninkmeijer, Carl A M

    2015-01-01

    Recent studies revealed layers of enhanced aerosol scattering in the upper troposphere and lower stratosphere over Asia (Asian Tropopause Aerosol Layer (ATAL)) and North America (North American Tropospheric Aerosol Layer (NATAL)). We use a sectional aerosol model (Community Aerosol and Radiation Model for Atmospheres (CARMA)) coupled with the Community Earth System Model version 1 (CESM1) to explore the composition and optical properties of these aerosol layers. The observed aerosol extinction enhancement is reproduced by CESM1/CARMA. Both model and observations indicate a strong gradient of the sulfur-to-carbon ratio from Europe to the Asia on constant pressure surfaces. We found that the ATAL is mostly composed of sulfates, surface-emitted organics, and secondary organics; the NATAL is mostly composed of sulfates and secondary organics. The model also suggests that emission increases in Asia between 2000 and 2010 led to an increase of aerosol optical depth of the ATAL by 0.002 on average which is consistent with observations. Key Points The Asian Tropopause Aerosol Layer is composed of sulfate, primary organics, and secondary organics The North American Tropospheric Aerosol Layer is mostly composed of sulfate and secondary organics Aerosol Optical Depth of Asian Tropopause Aerosol Layer increases by 0.002 from 2000 to 2010 PMID:26709320

  14. Variability in morphology, hygroscopicity, and optical properties of soot aerosols during atmospheric processing

    PubMed Central

    Zhang, Renyi; Khalizov, Alexei F.; Pagels, Joakim; Zhang, Dan; Xue, Huaxin; McMurry, Peter H.

    2008-01-01

    The atmospheric effects of soot aerosols include interference with radiative transfer, visibility impairment, and alteration of cloud formation and are highly sensitive to the manner by which soot is internally mixed with other aerosol constituents. We present experimental studies to show that soot particles acquire a large mass fraction of sulfuric acid during atmospheric aging, considerably altering their properties. Soot particles exposed to subsaturated sulfuric acid vapor exhibit a marked change in morphology, characterized by a decreased mobility-based diameter but an increased fractal dimension and effective density. These particles experience large hygroscopic size and mass growth at subsaturated conditions (<90% relative humidity) and act efficiently as cloud-condensation nuclei. Coating with sulfuric acid and subsequent hygroscopic growth enhance the optical properties of soot aerosols, increasing scattering by ≈10-fold and absorption by nearly 2-fold at 80% relative humidity relative to fresh particles. In addition, condensation of sulfuric acid is shown to occur at a similar rate on ambient aerosols of various types of a given mobility size, regardless of their chemical compositions and microphysical structures. Representing an important mechanism of atmospheric aging, internal mixing of soot with sulfuric acid has profound implications on visibility, human health, and direct and indirect climate forcing. PMID:18645179

  15. Variability in morphology, hygroscopicity, and optical properties of soot aerosols during atmospheric processing.

    PubMed

    Zhang, Renyi; Khalizov, Alexei F; Pagels, Joakim; Zhang, Dan; Xue, Huaxin; McMurry, Peter H

    2008-07-29

    The atmospheric effects of soot aerosols include interference with radiative transfer, visibility impairment, and alteration of cloud formation and are highly sensitive to the manner by which soot is internally mixed with other aerosol constituents. We present experimental studies to show that soot particles acquire a large mass fraction of sulfuric acid during atmospheric aging, considerably altering their properties. Soot particles exposed to subsaturated sulfuric acid vapor exhibit a marked change in morphology, characterized by a decreased mobility-based diameter but an increased fractal dimension and effective density. These particles experience large hygroscopic size and mass growth at subsaturated conditions (<90% relative humidity) and act efficiently as cloud-condensation nuclei. Coating with sulfuric acid and subsequent hygroscopic growth enhance the optical properties of soot aerosols, increasing scattering by approximately 10-fold and absorption by nearly 2-fold at 80% relative humidity relative to fresh particles. In addition, condensation of sulfuric acid is shown to occur at a similar rate on ambient aerosols of various types of a given mobility size, regardless of their chemical compositions and microphysical structures. Representing an important mechanism of atmospheric aging, internal mixing of soot with sulfuric acid has profound implications on visibility, human health, and direct and indirect climate forcing.

  16. Effect of Dust and Anthropogenic Aerosols on Columnar Aerosol Optical Properties over Darjeeling (2200 m asl), Eastern Himalayas, India

    PubMed Central

    Chatterjee, Abhijit; Ghosh, Sanjay K.; Adak, Anandamay; Singh, Ajay K.; Devara, Panuganti C. S.; Raha, Sibaji

    2012-01-01

    Background The loading of atmospheric particulate matter (aerosol) in the eastern Himalaya is mainly regulated by the locally generated anthropogenic aerosols from the biomass burning and by the aerosols transported from the distance sources. These different types of aerosol loading not only affect the aerosol chemistry but also produce consequent signature on the radiative properties of aerosol. Methodology/Principal Findings An extensive study has been made to study the seasonal variations in aerosol components of fine and coarse mode aerosols and black carbon along with the simultaneous measurements of aerosol optical depth on clear sky days over Darjeeling, a high altitude station (2200 masl) at eastern Himalayas during the year 2008. We observed a heavy loading of fine mode dust component (Ca2+) during pre-monsoon (Apr – May) which was higher by 162% than its annual mean whereas during winter (Dec – Feb), the loading of anthropogenic aerosol components mainly from biomass burning (fine mode SO42− and black carbon) were higher (76% for black carbon and 96% for fine mode SO42−) from their annual means. These high increases in dust aerosols during pre-monsoon and anthropogenic aerosols during winter enhanced the aerosol optical depth by 25 and 40%, respectively. We observed that for every 1% increase in anthropogenic aerosols, AOD increased by 0.55% during winter whereas for every 1% increase in dust aerosols, AOD increased by 0.46% during pre-monsoon. Conclusion/Significance The natural dust transport process (during pre-monsoon) plays as important a role in the radiation effects as the anthropogenic biomass burning (during winter) and their differential effects (rate of increase of the AOD with that of the aerosol concentration) are also very similar. This should be taken into account in proper modeling of the atmospheric environment over eastern Himalayas. PMID:22792264

  17. Simultaneous Retrieval of Aerosol and Surface Optical Properties from Combined Airborne- and Ground-Based Direct and Diffuse Radiometric Measurements

    NASA Technical Reports Server (NTRS)

    Gatebe, C. K.; Dubovik, O.; King, M. D.; Sinyuk, A.

    2010-01-01

    This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer (CAR) and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34-2.30 m) and angular range (180 ) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

  18. Ground-based Network and Supersite Measurements for Studying Aerosol Properties and Aerosol-Cloud Interactions

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee; Holben, Brent N.

    2008-01-01

    From radiometric principles, it is expected that the retrieved properties of extensive aerosols and clouds from reflected/emitted measurements by satellite (and/or aircraft) should be consistent with those retrieved from transmitted/emitted radiance observed at the surface. Although space-borne remote sensing observations contain large spatial domain, they are often plagued by contamination of surface signatures. Thus, ground-based in-situ and remote-sensing measurements, where signals come directly from atmospheric constituents, the sun, and the Earth-atmosphere interactions, provide additional information content for comparisons that confirm quantitatively the usefulness of the integrated surface, aircraft, and satellite datasets. The development and deployment of AERONET (AErosol RObotic NETwork) sunphotometer network and SMART-COMMIT (Surface-sensing Measurements for Atmospheric Radiative Transfer - Chemical, Optical & Microphysical Measurements of In-situ Troposphere) mobile supersite are aimed for the optimal utilization of collocated ground-based observations as constraints to yield higher fidelity satellite retrievals and to determine any sampling bias due to target conditions. To characterize the regional natural and anthropogenic aerosols, AERONET is an internationally federated network of unique sunphotometry that contains more than 250 permanent sites worldwide. Since 1993, there are more than 480 million aerosol optical depth observations and about 15 sites have continuous records longer than 10 years for annual/seasonal trend analyses. To quantify the energetics of the surface-atmosphere system and the atmospheric processes, SMART-COMMIT instrument into three categories: flux radiometer, radiance sensor and in-situ probe. Through participation in many satellite remote-sensing/retrieval and validation projects over eight years, SMART-COMMIT have gradually refine( and been proven vital for field deployment. In this paper, we will demonstrate the

  19. Observations of Aerosol Optical Properties over 15 AERONET Sites in Southeast Asia

    NASA Astrophysics Data System (ADS)

    Chan, J. D.; Lagrosas, N.; Uy, S. N.; Holben, B. N.; Dorado, S.; Tobias, V., Jr.; Anh, N. X.; Po-Hsiung, L.; Janjai, S.; Salinas Cortijo, S. V.; Liew, S. C.; Lim, H. S.; Lestari, P.

    2014-12-01

    Mean column-integrated optical properties from ground sun photometers of the Aerosol Robotic Network (AERONET) are studied to provide an overview of the characteristics of aerosols over the region as part of the 7 Southeast Asian Studies (7-SEAS) mission. The 15 AERONET sites with the most available level 2 data products are selected from Thailand (Chiang Mai, Mukdahan, Songkhla and Silpakorn University), Malaysia (University Sains Malaysia), Laos (Vientiane), Vietnam (Bac Giang, Bac Lieu and Nha Trang), Taiwan (National Cheng Kung University and Central Weather Bureau Taipei), Singapore, Indonesia (Bandung) and the Philippines (Manila Observatory and Notre Dame of Marbel University). For all 15 sites, high angstrom exponent values (α>1) have been observed. Chiang Mai and USM have the highest mean Angstrom exponent indicating the dominance of fine particles that can be ascribed to biomass burning and urbanization. Sites with the lowest Angstrom exponent values include Bac Lieu (α=1.047) and Manila Observatory (α=1.021). From the average lognormal size distribution curves, Songkhla and NDMU show the smallest annual variation in the fine mode region, indicating the observed fine aerosols are local to the sites. The rest of the sites show high variation which could be due to large scale forcings (e.g., monsoons and biomass burnings) that affect aerosol properties in these sites. Both high and low single scattering albedo at 440 nm (ω0440) values are found in sites located in major urban areas. Silpakorn University, Manila Observatory and Vientiane have all mean ω0440 < 0.90. Singapore and CWB Taipei have ω0440 > 0.94. The discrepancy in ω0 suggests different types of major emission sources present in urban areas. The absorptivity of urban aerosols can vary depending on the strength of traffic emissions, types of fuel combusted and automobile engines used, and the effect of biomass burning aerosols during the dry season. High aerosol optical depth values (τa550

  20. Optical and radiative properties of aerosols over Abu Dhabi in the United Arab Emirates

    NASA Astrophysics Data System (ADS)

    Beegum, S. Naseema; Romdhane, Haifa Ben; Ali, Mohammed Tauha; Armstrong, Peter; Ghedira, Hosni

    2016-12-01

    The present study is on the aerosol optical and radiative properties in the short-wave radiation and its climate implications at the arid city of Abu Dhabi (24.42 ∘N, 54.61 ∘E, 4.5 m MSL), in the United Arab Emirates. The direct aerosol radiative forcings (ARF) in the short-wave region at the top (TOA) and bottom of the atmosphere (BOA) are estimated using a hybrid approach, making use of discrete ordinate radiative transfer method in conjunction with the short-wave flux and spectral aerosol optical depth (AOD) measurements, over a period of 3 years (June 2012-July 2015), at Abu Dhabi located at the south-west coast of the Arabian Gulf. The inferred microphysical properties of aerosols at the measurement site indicate strong seasonal variations from the dominance of coarse mode mineral dust aerosols during spring (March-May) and summer (June-September), to the abundance of fine/accumulation mode aerosols mainly from combustion of fossil-fuel and bio-fuel during autumn (October-November) and winter (December-February) seasons. The monthly mean diurnally averaged ARF at the BOA (TOA) varies from -13.2 Wm-2 (˜-0.96 Wm-2) in November to -39.4 Wm-2 (-11.4 Wm-2) in August with higher magnitudes of the forcing values during spring/summer seasons and lower values during autumn/winter seasons. The atmospheric aerosol forcing varies from + 12.2 Wm-2 (November) to 28.2 Wm-2 (June) with higher values throughout the spring and summer seasons, suggesting the importance of mineral dust aerosols towards the solar dimming. Seasonally, highest values of the forcing efficiency at the surface are observed in spring (-85.0 ± 4.1 W m-2 τ -1) followed closely by winter (-79.2 ± 7.1 W m-2 τ -1) and the lowest values during autumn season (-54 ± 4.3 W m-2 τ -1). The study concludes with the variations of the atmospheric heating rates induced by the forcing. Highest heating rate is observed in June (0.39 K day -1) and the lowest in November (0.17 K day -1) and the temporal

  1. Atmospheric correction of ocean color imagery: use of the junge power-law aerosol size distribution with variable refractive index to handle aerosol absorption.

    PubMed

    Chomko, R M; Gordon, H R

    1998-08-20

    When strongly absorbing aerosols are present in the atmosphere, the usual two-step procedure of processing ocean color data-(1) atmospheric correction to provide the water-leaving reflectance (rho(w)), followed by (2) relating rho(w) to the water constituents-fails and simultaneous estimation of the ocean and aerosol optical properties is necessary. We explore the efficacy of using a simple model of the aerosol-a Junge power-law size distribution consisting of homogeneous spheres with arbitrary refractive index-in a nonlinear optimization procedure for estimating the relevant oceanic and atmospheric parameters for case 1 waters. Using simulated test data generated from more realistic aerosol size distributions (sums of log-normally distributed components with different compositions), we show that the ocean's pigment concentration (C) can be retrieved with good accuracy in the presence of weakly or strongly absorbing aerosols. However, because of significant differences in the scattering phase functions for the test and power-law distributions, large error is possible in the estimate of the aerosol optical thickness. The positive result for C suggests that the detailed shape of the aerosol-scattering phase function is not relevant to the atmospheric correction of ocean color sensors. The relevant parameters are the aerosol single-scattering albedo and the spectral variation of the aerosol optical depth. We argue that the assumption of aerosol sphericity should not restrict the validity of the algorithm and suggest an avenue for including colored aerosols, e.g., wind-blown dust, in the procedure. A significant advantage of the new approach is that realistic multicomponent aerosol models are not required for the retrieval of C.

  2. Viscosity and electric properties of water aerosols

    NASA Astrophysics Data System (ADS)

    Shavlov, A. V.; Sokolov, I. V.; Dzhumandzhi, V. A.

    2016-09-01

    The flow of water mist in a narrow duct has been studied experimentally. The profile of the velocity of drops has been measured, and the viscosity of the mist has been calculated using the Navier-Stokes equation. It has been found that at low gradients of the rate of shear the viscosity of the mist can exceed that of clean air by tens and even hundreds of times. The electric charge of the drops has been measured. It has been found that the viscosity of the mist differs from that of clean air at gradients of the rate of shear that are less than the frequency of the establishment of electric equilibrium between the drops. A comparative analysis of the viscosities of the mist and a drop cluster has been carried out, and the dependence of the viscosity of the water aerosol on the radius and the charge of the drops has been predicted. The possible role of aerosols that contain submicron drops in the known "clear air turbulence" problem has been shown.

  3. Retrieval of Aerosol Optical Properties under Thin Cirrus from MODIS

    NASA Technical Reports Server (NTRS)

    Lee, Jaehwa; Hsu, Nai-Yung Christina; Bettenhausen, Corey; Sayer, Andrew Mark.

    2014-01-01

    Retrieval of aerosol optical properties using shortwave bands from passive satellite sensors, such as MODIS, is typically limited to cloud-free areas. However, if the clouds are thin enough (i.e. thin cirrus) such that the satellite-observed reflectance contains signals under the cirrus layer, and if the optical properties of this cirrus layer are known, the TOA reflectance can be corrected for the cirrus layer to be used for retrieving aerosol optical properties. To this end, we first correct the TOA reflectances in the aerosol bands (0.47, 0.55, 0.65, 0.86, 1.24, 1.63, and 2.12 micron for ocean algorithm and 0.412, 0.47, and 0.65 micron for deep blue algorithm) for the effects of thin cirrus using 1.38 micron reflectance and conversion factors that convert cirrus reflectance in 1.38 micron band to those in aerosol bands. It was found that the conversion factors can be calculated by using relationships between reflectances in 1.38 micron band and minimum reflectances in the aerosol bands (Gao et al., 2002). Refer to the example in the figure. Then, the cirrus-corrected reflectance can be calculated by subtracting the cirrus reflectance from the TOA reflectance in the optically thin case. A sensitivity study suggested that cloudy-sky TOA reflectances can be calculated with small errors in the form of simple linear addition of cirrus-only reflectances and clear-sky reflectances. In this study, we correct the cirrus signals up to TOA reflectance at 1.38 micron of 0.05 where the simple linear addition is valid without extensive radiative transfer simulations. When each scene passes the set of tests shown in the flowchart, the scene is corrected for cirrus contamination and passed into aerosol retrieval algorithms.

  4. Reduction of Aerosol Absorption in Beijing Since 2007 from MODIS and AERONET

    NASA Technical Reports Server (NTRS)

    Lyapustin, A.; Smirnov, A.; Holben, B.; Chin, M.; Streets, D. G.; Lu, Z.; Kahn, R.; Slutsker, I.; Laszlo, I.; Kondragunta, S.; Tanre, D.; Dubovik, O.; Goloub, P.; Chen, H.-B.; Sinyuk, A.; Wang, Y.; Korkin, S.

    2011-01-01

    An analysis of the time series of MODIS-based and AERONET aerosol records over Beijing reveals two distinct periods, before and after 2007. The MODIS data from both the Terra and Aqua satellites were processed with the new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. A comparison of MAIAC and AERONET AOT shows that whereas MAIAC consistently underestimated peak AOT values by 10-20% in the prior period, the bias mostly disappears after mid- 2007. Independent analysis of the AERONET dataset reveals little or no change in the effective radii of the fine and coarse fractions and of the Angstrom exponent. At the same time, it shows an increasing trend in the single scattering albedo, by 0.02 in 9 years. As MAIAC was using the same aerosol model for the entire 2000-2010 period, the decrease in AOT bias after 2007 can be explained only by a corresponding decrease of aerosol absorption caused by a reduction in local black carbon emissions. The observed changes correlate in time with the Chinese government's broad measures to improve air quality in Beijing during preparations for the Summer Olympics of 2008.

  5. Reduction of Aerosol Absorption in Beijing Since 2007 from MODIS and AERONET

    NASA Technical Reports Server (NTRS)

    Lyapustin, A.; Smirnov, A.; Holben, B.; Chin, M.; Streets, D. G.; Lu, Z.; Kahn, R.; Slutsker, I.; Laszlo, I.; Kondragunta, S.; Tanre, D.; Dubovik, O.; Goloub, P.; Chen, H.-B.; Sinyuk, A.; Wang, Y.; Korkin, S.

    2011-01-01

    An analysis of the time series of MODIS-based and AERONET aerosol records over Beijing reveals two distinct periods, before and after 2007. The MODIS data from both the Terra and Aqua satellites were processed with the new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. A comparison of MAIAC and AERONET AOT shows that whereas MAIAC consistently underestimated peak AOT values by 10-20% in the prior period, the bias mostly disappears after mid-2007. Independent analysis of the AERONET dataset reveals little or no change in the effective radii of the fine and coarse fractions and of the Angstrom exponent. At the same time, it shows an increasing trend in the single scattering albedo, by approx.0.02 in 9 years. As MAIAC was using the same aerosol model for the entire 2000-2010 period, the decrease in AOT bias after 2007 can be explained only by a corresponding decrease of aerosol absorption caused by a reduction in local black carbon emissions. The observed changes correlate in time with the Chinese government's broad measures to improve air quality in Beijing during preparations for the Summer Olympics of 2008.

  6. Laboratory Measurement of the Optical Properties of Hematite and Desert Dust Aerosols to Assess Their Climate Forcing

    NASA Astrophysics Data System (ADS)

    Moosmuller, H.; Aiken, A. C.; Dubey, M. K.; Frey, G.; Garro, B.; Engelbrecht, J. P.

    2012-12-01

    Globally, aerosol mass emissions and optical depths are dominated by entrained mineral dust. While most minerals occurring in dust aerosols do not absorb solar radiation, some minerals cause significant absorption, thereby lowering the single scatter albedo (SSA) significantly below one, potentially contributing to a warmer and drier atmosphere. Therefore, the optical properties of globally relevant dust aerosols need to be characterized to reduce uncertainties in their radiative forcings. A well-known absorbing component found in dust aerosols is hematite, Fe2O3, which absorbs strongly in the blue-green spectral region, giving some soils, rocks, and dust aerosols their characteristic red color. We discuss measurements of the optical properties of ~30 dust aerosols, including a pure hematite standard, hematite-containing mineral dust standards ranging from 9-34% hematite by mass, and various dust samples collected from around the world. Samples are suspended from aqueous solution and/or from dry atomization with a cyclone re-suspension chamber yielding the fine fraction relevant for long-range transport. Size distributions were characterized with an optical aerosol spectrometer; absorption and scattering coefficients were measured with a three-wavelength photoacoustic soot spectrometer (PASS-3) at 405, 532, and 781 nm and with an ultraviolet photoacoustic soot spectrometer (PASS-UV) at 375 nm yielding wavelength-dependent mass absorption coefficients (MAC's), SSA's, and wavelength dependent Angstrom exponents. Hematite MAC's are an order of magnitude smaller than those of black carbon (BC) at 405 nm and 532 nm and are largely non-absorbing at 781 nm with SSA's of 0.49 0.68 and 0.98, respectively.

  7. Estimate of the aerosol properties over the ocean with POLDER

    NASA Astrophysics Data System (ADS)

    Deuzé, J. L.; Goloub, P.; Herman, M.; Marchand, A.; Perry, G.; Susana, S.; Tanré, D.

    2000-06-01

    The wide field of view imaging spectroradiometer Polarization and Directionality of the Earth's Reflectance (POLDER) developed by Centre National d'Etudes Spatiales and operated aboard the Japanese heliosynchronous platform Advanced Earth Observation Satellite (ADEOS) from October 30, 1996, to June 30, 1997, provided the first global systematic measurements of the spectral, directional, and polarized characteristics of the solar radiation reflected by the Earth/atmosphere system. These original observational capabilities offer an opportunity to enhance the characterization of several components of the global environment, especially the oceanic and terrestrial vegetal primary production, the aerosol physical and optical properties, and the tridimensional structure and microphysics of clouds. Here we examine the remote sensing of aerosols over the oceans. In a first step the aerosol optical thickness and Ångström exponent are derived from the radiance measurements. In a second step the polarization measurements are used for the retrieval of the aerosol refractive index. The inversion algorithm assumes spherical, nonabsorbing particles with monomodal lognormal size distribution. The adequacy of this modeling is discussed for a representative set of aerosol observations. Successful retrieval is generally achieved in the presence of small aerosols with Ångström exponent larger than ˜1.0. For such particles, polarization may provide information on the particle refractive index. As the Ångstrom exponent of the particle decreases, the data fitting residual errors increase, especially in polarized light, which prevents the retrieval of the aerosol refractive index. The trends of the discrepancies point out two shortcomings of the aerosol modeling. The theoretical results systematically underestimate the contribution of small polarizing particles in the polarization measurements for side-scattering angles ranging from 80° to 120°. This indicates very probably that

  8. Investigation on seasonal variations of aerosol properties and its influence on radiative effect over an urban location in central India

    NASA Astrophysics Data System (ADS)

    Jose, Subin; Gharai, Biswadip; Niranjan, K.; Rao, P. V. N.

    2016-05-01

    Aerosol plays an important role in modulating solar radiation, which are of great concern in perspective of regional climate change. The study analysed the physical and optical properties of aerosols over an urban area and estimated radiative effect using three years in-situ data from sunphotometer, aethalometer and nephelometer as input to radiative transfer model. Aerosols properties indicate the dominance of fine mode aerosols over the study area. However presence of coarse mode aerosols is also found during pre-monsoon [March-April-May]. Daily mean aerosol optical depth showed a minimum during winter [Dec-Jan-Feb] (0.45-0.52) and a maximum during pre-monsoon (0.6-0.7), while single scattering albedo (ω) attains its maximum (0.78 ± 0.05) in winter and minimum (0.67 ± 0.06) during pre-monsoon and asymmetry factor varied in the range between 0.48 ± 0.02 to 0.53 ± 0.04. Episodic events of dust storm and biomass burning are identified by analyzing intrinsic aerosol optical properties like scattering Ångström exponent (SAE) and absorption Ångström exponent (AAE) during the study periods and it has been observed that during dust storm events ω is lower (˜0.77) than that of during biomass burning (˜0.81). The aerosol direct radiative effect at top of the atmosphere during winter is -11.72 ± 3.5 Wm-2, while during pre-monsoon; it is -5.5 ± 2.5 Wm-2, which can be due to observed lower values of ω during pre-monsoon. A large positive enhancement of atmospheric effect of ˜50.53 Wm-2 is observed during pre-monsoon compared to winter. Due to high aerosol loading in pre-monsoon, a twofold negative surface forcing is also observed in comparison to winter.

  9. Effect of aging on morphology, hygroscopicity, and optical properties of soot aerosol

    NASA Astrophysics Data System (ADS)

    Khalizov, A. F.; Xue, H.; Pagels, J.; McMurry, P. H.; Zhang, R.

    2009-12-01

    Soot from incomplete combustion represents one of the major forms of particulate matter pollution, profoundly impacting human health, air quality, and climate. The direct and indirect radiative effects of soot aerosol depend on particle composition and morphology, which may vary significantly when aerosol is subjected to atmospheric aging. We will present an overview of a comprehensive set of experimental measurements performed in our laboratory at Texas A&M to study the effect of internal mixing with atmospheric species on morphology, hygroscopicity, and optical properties of combustion soot. In our experiments, size-classified soot aerosol was exposed to 0.1 - 1000 ppb (part per billion) mixing ratios of sulfuric acid and dicarboxylic organic acids and resulting changes particle morphology and mixing state under dry and humid conditions were characterized through mass-mobility measurements by aerosol particle mass analyzer (APM) and tandem differential mobility analyzer (TDMA). Light absorption and scattering cross-sections for well-characterized fresh and coated soot aerosol were derived using a cavity ring-down spectrometer and an integrating nephelometer in order to assess the effect of atmospheric processing on the radiative properties of atmospheric soot. Internally mixed soot shows significant changes in particle morphology, increasing with the mass fraction of the coating material and relative humidity. Restructuring was the strongest for aggregates coated by sulfuric and glutaric acids whereas succinic acid coating did not result in observable morphology change. Sulfuric acid - coated particles experienced large hygroscopic growth at sub-saturated conditions and activated to cloud droplets at atmospherically relevant supersaturations. Furthermore, coating and subsequent hygroscopic growth considerably altered the optical properties of soot aerosol, increasing light scattering and absorption cross-sections. We found that irreversible restructuring of soot

  10. In situ airborne measurements of aerosol optical properties during photochemical pollution events

    NASA Astrophysics Data System (ADS)

    Mallet, M.; van Dingenen, R.; Roger, J. C.; Despiau, S.; Cachier, H.

    2005-02-01

    Dry aerosol optical properties (scattering, absorbing coefficients, and single scattering albedo) were derived from in situ airborne measurements during two photochemical pollution events (25 and 26 June) observed during the Experience sur Site pour Contraindre les Modeles de Pollution atmospherique et de Transport d'Emissions (ESCOMPTE) experiment. Two flights were carried out during daytime (one during the morning and one at noon) over a domain, allowing the investigation of how an air pollution event affects the particle optical properties. Both horizontal distribution and vertical profiles are presented. Results from the horizontal mapping show that plumes of enhanced scattering and absorption are formed in the planetary boundary layer (PBL) during the day in the sea breeze-driven outflow of the coastal urban-industrial area of Marseille-Fos de Berre. The domain-averaged scattering coefficient (at 550 nm) over land σs changes from 35 (28) Mm-1 during land breeze to 63 (43) Mm-1 during sea breeze on 25 June (26 June), with local maxima reaching > 100 Mm-1. The increase in the scattering coefficient is associated with new particle formation, indicative of secondary aerosol formation. Simultaneously, the domain-averaged absorption coefficient increases from 5.6 (3.4) Mm-1 to 9.3 (8.0) Mm-1. The pollution plume leads to strong gradients in the single scattering albedo ωo over the domain studied, with local values as low as 0.73 observed inside the pollution plume. The role of photochemistry and secondary aerosol formation during the 25 June case is shown to increase ωo and to make the aerosol more `reflecting' while the plume moves away from the sources. The lower photochemical activity, observed in the 26 June case, induces a relatively higher contribution of black carbon, making the aerosol more absorbing. Results from vertical profiles at a single near-urban location in the domain indicate that the changes in optical properties happen almost entirely within

  11. Aerosol Properties From Combined Oxygen A Band Radiances and Lidar

    NASA Technical Reports Server (NTRS)

    Winker, Dave; Zhai, Peng-Wang; Hu, Yongxiang

    2015-01-01

    We have developed a new aerosol retrieval technique based on combing high-resolution A band spectra with lidar profiles. Our goal is the development of a technique to retrieve aerosol absorption, one of the critical parameters affecting the global radiation budget and one which is currently poorly constrained by satellite measurements. Our approach relies on two key factors: 1) the use of high spectral resolution (17,000:1) measurements which resolve the A-band line structure, and 2) the use of co-located lidar profile measurements to constrain the vertical distribution of scatterers in the forward model. The algorithm has been developed to be applied to observations from the CALIPSO and OCO-2 satellites, flying in formation as part of the A-train constellation. We describe the approach and present simulated retrievals to illustrate performance potential.

  12. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols.

    PubMed

    Higdon, N S; Browell, E V; Ponsardin, P; Grossmann, B E; Butler, C F; Chyba, T H; Mayo, M N; Allen, R J; Heuser, A W; Grant, W B; Ismail, S; Mayor, S D; Carter, A F

    1994-09-20

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H(2)O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and > 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H(2)O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H(2)O absorption-line parameters were perfo med to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H(2)O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H(2)O radiosondes. The H(2)O distributions measured with the DIAL system differed by ≤ 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  13. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols

    NASA Technical Reports Server (NTRS)

    Carter, Arlen F.; Allen, Robert J.; Mayo, M. Neale; Butler, Carolyn F.; Grossman, Benoist E.; Ismail, Syed; Grant, William B.; Browell, Edward V.; Higdon, Noah S.; Mayor, Shane D.; Ponsardin, Patrick; Hueser, Alene W.

    1994-01-01

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H2O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and greater than 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H2O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H2O absorption-line parameters were performed to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H2O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H2O radiosondes. The H2O distributions measured with the DIAL system differed by less than 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  14. Large-scale enhancement in aerosol absorption in the lower free troposphere over continental India during spring

    NASA Astrophysics Data System (ADS)

    Nair, Vijayakumar S.; Babu, S. Suresh; Gogoi, Mukunda M.; Moorthy, K. Krishna

    2016-11-01

    Aerosol absorption in the lower troposphere over continental India was assessed using extensive measurements of the vertical distribution of absorption coefficients aboard an instrumented aircraft. Measurements were made from seven base stations during winter (November-December 2012) and spring (April-May 2013), supplemented by the data from the networks of surface observatories. A definite enhancement in aerosol absorption has been observed in the lower free troposphere over the Indo-Gangetic Plain (IGP) during spring, along with a reduction near the surface. The regional mean aerosol absorption optical depth (AAOD) over IGP, which was derived from aircraft observations (integrated from the ground to 3 km), increased from 0.020 ± 0.009 in winter to 0.048 ± 0.01 in spring. The columnar AAOD depicted weak and distinctly different seasonal variations than that of surface level black carbon mass concentrations. This contrasting difference in the seasonality indicates the presence of elevated layers of absorbing aerosols during spring in association with the long-range transport and vertical convective lofting of aerosols.

  15. Cavity Ring-Down Measurement of Aerosol Optical Properties During the Asian Dust Above Monterey Experiment and DOE Aerosol Intensive Operating Period

    NASA Technical Reports Server (NTRS)

    Ricci, K.; Strawa, A. W.; Provencal, R.; Castaneda, R.; Bucholtz, A.; Schmid, B.

    2004-01-01

    Large uncertainties in the effects of aerosols on climate require improved in-situ measurements of extinction coefficient and single-scattering albedo. This paper describes preliminary results from Cadenza, a new continuous wave cavity ring-down (CW-CRD) instrument designed to address these uncertainties. Cadenza measures the aerosol extinction coefficient for 675 nm and 1550 nm light, and simultaneously measures the scattering coefficient at 675 nm. In the past year Cadenza was deployed in the Asian Dust Above Monterey (ADAM) and DOE Aerosol Intensive Operating Period (IOP) field projects. During these flights Cadenza produced measurements of aerosol extinction in the range from 0.2 to 300/Mm with an estimated precision of 0.1/Mm for 1550 nm light and 0.2/Mm for 675 nm light. Cadenza data from the ADAM and Aerosol IOP missions compared favorably with data from the other instruments aboard the CIRPAS Twin Otter aircraft and participating in those projects. We present comparisons between the Cadenza measurements and those from a TSI nephelometer, Particle Soot Absorption Photometer (PSAP), and the AATS 14 sun-photometer. Measurements of the optical properties of smoke and dust plumes sampled during these campaigns are presented and estimates of heating rates due to these plumes are made.

  16. Hygroscopic properties of different aerosol types over the Atlantic and Indian Oceans

    NASA Astrophysics Data System (ADS)

    Maßling, A.; Wiedensohler, A.; Busch, B.; Neusüß, C.; Quinn, P.; Bates, T.; Covert, D.

    2003-09-01

    Hygroscopic properties of atmospheric particles were studied in the marine tropospheric boundary layer over the Atlantic and Indian Oceans during two consecutive field studies: the Aerosols99 cruise (Atlantic Ocean) from 15 January to 20 February 1999, and the INDOEX cruise (Indian Ocean Experiment) from 23 February to 30 March 1999. The hygroscopic properties were compared to optical and chemical properties, such as absorption, chemical inorganic composition, and mass concentration of organic and elemental carbon, to identify the influence of these parameters on hygroscopicity. During the two field studies, four types of aerosol-sampling instruments were used on board the NOAA (National Oceanic and Atmospheric Administration) Research Vessel Ronald H. Brown: Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA), seven-stage cascade impactor, two-stage cascade impactor, and Particle Soot Absorption Photometer (PSAP). The HTDMA was used to determine the hygroscopic properties of atmospheric particles at initial dry sizes (Dp) of 50, 150, and 250 nm and at relative humidities (RH) of 30, 55, 75, and 90%. Simultaneously, a seven-stage cascade impactor of which 3 stages were in the sub-mm size range was used to determine the molar composition of the major inorganic ions such as ammonium and sulfate ions. A two-stage cascade impactor (1 in the sub-mm size range, 1 in the sup-mm size range) was used to determine the mass concentration of organic and elemental carbon. The PSAP was used (at a wavelength of 565 nm) to measure the light absorption coefficient of the aerosol. During the two field studies, air masses of several different origins passed the ship's cruise path. The occurrence of different air masses was classified into special time periods signifying the origin of the observed aerosol. All time periods showed a group of particles with high hygroscopic growth. The measured average hygroscopic growth factors defined by the ratio of dry and wet particle

  17. Simultaneous retrieval of aerosol properties and clear-sky direct radiative effect over the global ocean from MODIS

    NASA Astrophysics Data System (ADS)

    Lee, Jaehwa; Kim, Jhoon; Lee, Yun Gon

    2014-08-01

    A unified satellite algorithm is presented to simultaneously retrieve aerosol properties (aerosol optical depth; AOD and aerosol type) and clear-sky shortwave direct radiative effect (hereafter, DREA) over ocean. The algorithm is applied to Moderate Resolution Imaging spectroradiometer (MODIS) observations for a period from 2003 to 2010 to assess the DREA over the global ocean. The simultaneous retrieval utilizes lookup table (LUT) containing both spectral reflectances and solar irradiances calculated using a single radiative transfer model with the same aerosol input data. This study finds that aerosols cool the top-of-atmosphere (TOA) and bottom-of-atmosphere (BOA) by 5.2 ± 0.5 W/m2 and 8.3 W/m2, respectively, and correspondingly warm the atmosphere (hereafter, ATM) by 3.1 W/m2. These quantities, solely based on the MODIS observations, are consistent with those of previous studies incorporating chemical transport model simulations and satellite observations. However, the DREAs at BOA and ATM are expected to be less accurate compared to that of TOA due to low sensitivity in retrieving aerosol type information, which is related with the atmospheric heating by aerosols, particularly in low AOD conditions; consequently, the uncertainties could not be quantified. Despite the issue in the aerosol type information, the present method allows us to confine the DREA attributed only to fine-mode dominant aerosols, which are expected to be mostly anthropogenic origin, in the range from -1.1 W/m2 to -1.3 W/m2 at TOA. Improvements in size-resolved AOD and SSA retrievals from current and upcoming satellite instruments are suggested to better assess the DREA, particularly at BOA and ATM, where aerosol absorptivity induces substantial uncertainty.

  18. Observations of aerosol optical properties at a coastal site in Hong Kong, South China

    NASA Astrophysics Data System (ADS)

    Wang, Jiaping; Virkkula, Aki; Gao, Yuan; Lee, Shuncheng; Shen, Yicheng; Chi, Xuguang; Nie, Wei; Liu, Qiang; Xu, Zheng; Huang, Xin; Wang, Tao; Cui, Long; Ding, Aijun

    2017-02-01

    Temporal variations in aerosol optical properties were investigated at a coastal station in Hong Kong based on the field observation from February 2012 to February 2015. At 550 nm, the average light-scattering (151 ± 100 Mm-1) and absorption coefficients (8.3 ± 6.1 Mm-1) were lower than most of other rural sites in eastern China, while the single-scattering albedo (SSA = 0.93 ± 0.05) was relatively higher compared with other rural sites in the Pearl River Delta (PRD) region. Correlation analysis confirmed that the darkest aerosols were smaller in particle size and showed strong scattering wavelength dependencies, indicating possible sources from fresh emissions close to the measurement site. Particles with Dp of 200-800 nm were less in number, yet contributed the most to the light-scattering coefficients among submicron particles. In summer, both ΔBC / ΔCO and SO2 / BC peaked, indicating the impact of nearby combustion sources on this site. Multi-year backward Lagrangian particle dispersion modeling (LPDM) and potential source contribution (PSC) analysis revealed that these particles were mainly from the air masses that moved southward over Shenzhen and urban Hong Kong and the polluted marine air containing ship exhausts. These fresh emission sources led to low SSA during summer months. For winter and autumn months, contrarily, ΔBC / ΔCO and SO2 / BC were relatively low, showing that the site was more under influence of well-mixed air masses from long-range transport including from South China, East China coastal regions, and aged aerosol transported over the Pacific Ocean and Taiwan, causing stronger abilities of light extinction and larger variability of aerosol optical properties. Our results showed that ship emissions in the vicinity of Hong Kong could have visible impact on the light-scattering and absorption abilities as well as SSA at Hok Tsui.

  19. Influence of Delhi Pollution on Aerosol Properties Over Greater Noida

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Singh, R. P.; Kumar, R.

    2015-12-01

    Influence of Delhi Pollution on Aerosol Properties over Greater NoidaManish Sharma1, Ramesh P. Singh2 and Rajesh Kumar3 1Research and Technology Development Centre, Sharda University, Greater Noida, India. 2School of Earth and Environmental Sciences, Schmid College of Science, Chapman University, Orange 92866, USA 3School of Basic Sciences and Research, Sharda University, Greater Noida, India. Delhi capital of India is highly polluted during winter and summer seasons. Due to dominant westerly winds the air mass influence its neighboring city Greater Noida which is located 60 km south east of Delhi. Detailed analysis of multi satellite data and ground observations have been carried out during 2001-2015. The ground observation and satellite data show dynamic aerosol optical parameters over Greater Noida. During winter and summer seasons, dominant westerly wind outflow pollutants of Delhi that mix with the local anthropogenic emissions of Greater Noida influencing aerosol properties at different pressure levels. The characteristics of trace gases and aerosol parameters over Delhi and Greater Noida will be presented. The air quality is severely affected from the outflow of pollutants from Delhi which is threat to people living in the area. Due to dominant winds the air mass further transported towards eastern parts of Indo-Gangetic plains affecting weather conditions of the major cities.

  20. Seasonal variability of optical properties of aerosols in the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Vrekoussis, M.; Liakakou, E.; Koçak, M.; Kubilay, N.; Oikonomou, K.; Sciare, J.; Mihalopoulos, N.

    The aerosol optical properties (scattering and absorption coefficients) were investigated at two remote locations in the Eastern Mediterranean in conjunction with aerosol ion composition measurements: Finokalia in the Crete Island in Greece (March 2001-June 2002) and Erdemli in Turkey (July 1999-June 2000). Ambient light-scattering coefficient ( σsp-532 nm ) at Finokalia had a mean value of 50±23 Mm -1 while at Erdemli this value was 90±160 Mm -1, due to a severe dust event that occurred from 17 to 19 April 2000. Scattering coefficients up to 5000 Mm -1 were encountered during the transition periods (spring and autumn) and were associated with dust storm events. During these events significant correlations were observed between dust and σsp and mass scattering efficiencies of 0.21 and 0.96 m 2g -1 were calculated for dust for Finokalia and Erdemli, respectively. Significant correlations were also observed at both locations between non-sea-salt sulphate (nss-SO 42-); σsp and mass scattering efficiencies of 5.9±1.8 and 5.7±1.4 m 2g -1 were calculated for the nss-SO 42- at Finokalia and Erdemli, respectively. At Finokalia absorption measurements were also performed at the same time and the mean absorption coefficient ( σap-565 nm ) was found to be 5.6±3.6 Mm -1. Maxima of absorption coefficient were associated with two distinct meteorological situations indicative of pollution transported from northern Europe and Saharan dust events. Saharan dust can therefore significantly contribute to both scattering and absorption of solar radiation, the latter due to its hematite content. Based on scattering and absorption measurements, an annual mean single-scattering albedo ( ω) adjusted at 550 nm of 0.89±0.04 was calculated for Finokalia. Finally, radiative forcing efficiency (RFE) over the sea at 550 nm induced by aerosols has been calculated for Finokalia. RFE follows a clear seasonal variation, with the lowest mean values during summer (-73W m -2) and the highest

  1. Aerosol Light Absorption and Scattering in Mexico City: Comparison With Las Vegas, NV, and Los Angeles, CA.

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, G.; Arnott, W. P.; Gaffney, J. S.; Marley, N. A.; Campbell, D.; Fujita, E.

    2007-12-01

    Aerosol light scattering and absorption measurements were deployed in and near Mexico City in March 2006 as part of the Megacity Impacts on Regional and Global Environments (MIRAGE). The primary site in Mexico City was an urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP). Similar campaigns were held in Las Vegas, NV in January-February, 2003; and Los Angeles, CA at numerous sites during all seasons from 2003 through 2007. The IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions. The photoacoustic instrument (PAS) used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In Mexico City the aerosol absorption coefficient typically varies between 20 and 180 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed probably as a consequence of secondary aerosol formation. We will present the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the IMP site and compare with Las Vegas diurnal variation. Mexico City 'breaths' more during the course of the day than Las Vegas, Nevada in part because the latitude of Mexico City resulted in more direct solar radiation. Further insight on the meteorological connections and population dynamics will be discussed.

  2. Aerosols physical properties at Hada Al Sham, western Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Lihavainen, H.; Alghamdi, M. A.; Hyvärinen, A.-P.; Hussein, T.; Aaltonen, V.; Abdelmaksoud, A. S.; Al-Jeelani, H.; Almazroui, M.; Almehmadi, F. M.; Al Zawad, F. M.; Hakala, J.; Khoder, M.; Neitola, K.; Petäjä, T.; Shabbaj, I. I.; Hämeri, K.

    2016-06-01

    This is the first time to clearly derive the comprehensive physical properties of aerosols at a rural background area in Saudi Arabia. Aerosol measurements station was established at a rural background area in the Western Saudi Arabia to study the aerosol properties. This study gives overview of the aerosol physical properties (PM10, PM2.5, black carbon and total number concentration) over the measurement period from November 2012 to February 2015. The average PM10 and PM2.5 concentrations were 95 ± 78 μg m-3 (mean ± STD, at ambient conditions) and 33 ± 68 μg m-3 (at ambient conditions), respectively. As expected PM10 concentration was dominated by coarse mode particles (PM10-PM2.5), most probably desert dust. Especially from February to June the coarse mode concentrations were high because of dust storm season. Aerosol mass concentrations had clear diurnal cycle. Lower values were observed around noon. This behavior is caused by wind direction and speed, during night time very calm easterly winds are dominating whereas during daytime the stronger westerly winds are dominating (sea breeze). During the day time the boundary layer is evolving, causing enhanced mixing and dilution leading to lower concentration. PM10 and PM2.5 concentrations were comparable to values measured at close by city of Jeddah. Black carbon concentration was about 2% and 6% of PM10 and PM2.5 mass, respectively. Total number concentration was dominated by frequent new particle formation and particle growth events. The typical diurnal cycle in particle total number concentration was clearly different from PM10 and PM2.5.

  3. Urban aerosol radiative properties: Measurements during the 1999 Atlanta Supersite Experiment

    NASA Astrophysics Data System (ADS)

    Carrico, Christian M.; Bergin, Michael H.; Xu, Jin; Baumann, Karsten; Maring, Hal

    2003-04-01

    As part of the Atlanta Supersite 1999 study, aerosol radiative and related physical and chemical properties are examined on the basis of measurements of PM2.5 (aerosol particles with aerodynamic diameters, Dp, less than 2.5 μm) in urban Atlanta. In addition to potential compliance issues with proposed regulatory standards, PM2.5 concentrations in Atlanta and the surrounding region are large enough to have an important impact on atmospheric radiative transfer and hence visibility and potentially regional climate. Arithmetic means and standard deviations of the light scattering by PM2.5 (σsp at 530 nm) and absorption coefficients (σap at 550 nm) measured at a controlled relative humidity of 49 ± 5% are 121 ± 48 and 16 ± 12 Mm-1, respectively. Though the mean light extinction coefficient (σep) in Atlanta is much larger than background sites, it is comparable to nonurban areas in the interior southeast United States highlighting the contribution of a regional haze here. The single scattering albedo (ωo) in Atlanta is 0.87 ± 0.08 and is ˜10% lower than reported in nonurban polluted sites, likely a result of the emission of elemental carbon (EC) from mobile sources. A pronounced diel pattern in aerosol properties is observed with clear influences from mobile sources (morning rush hour maxima in concentrations, particularly soot-related indicators) and atmospheric mixing (afternoon minima). A strong linear relationship between σsp and PM2.5 is observed, and using several techniques, gives a range of mean mass scattering efficiencies (Esp) from = 3.5 to 4.4 m2 g-1. EC and σap are observed to have a relationship though less strongly correlated than σsp and PM2.5. Four methods of determining the mass absorption efficiency of EC give Eap ranging from 5.3 to 18.3 m2 g-1. This wide range of values is a result of the variability in aerosol properties, uncertainties in the light absorption method, and in particular, differences in the EC measurement techniques. Best

  4. Direct effect of aerosol optical properties on global dimming and brightening

    NASA Astrophysics Data System (ADS)

    Kudo, R.; Uchiyama, A.

    2011-12-01

    Surface solar radiation observed at numerous locations has decreased from the 1960s to the 1980s (Global dimming), thereafter increased (Global brightening). The dimming and brightening is considered to be due to the changes in both clouds and aerosols. Aerosols have a direct impact on the surface solar radiation by scattering and absorption. The impact is determined by three parameters: optical depth (AOD), single scattering albedo (SSA), and asymmetry factor, but the effect of asymmetry factor is rather smaller than the others. Therefore, the long-term changes in AOD and SSA are necessary to evaluate the aerosol impact on the global dimming and brightening. We have developed the method to estimate AOD and SSA from the hourly accumulated direct and diffuse irradiances measured by the ground-based broadband radiometers. In the estimation, the real part of the refractive index is fixed, and the size distribution is defined by the Junge distribution with a fixed shaping constant. Using the developed method, the measurements from 1975 to 2008 at 14 sites in Japan were analyzed. Consequently, a decrease of AOD by 0.02 and an increase of SSA by 0.2 during the period were seen. The surface solar radiation under the clear sky conditions, which was calculated from the estimated aerosol optical properties, was increased by 5% due to the changes in AOD and SSA; the influence of SSA was dominant. We also investigate the cloud impact on the surface solar radiation which was simply defined as the difference between the surface solar radiation under the cloudy sky conditions and under the clear sky conditions; the cloud impact had no statistically significant trends. The brightening in Japan may be due to the changes in aerosol optical properties, especially SSA. Our developed method can be applied to measurements at other sites around the world and would be helpful to understand the causes of the global dimming and brightening.

  5. The filter-loading effect by ambient aerosols in filter absorption photometers depends on the coating of the sampled particles

    NASA Astrophysics Data System (ADS)

    Drinovec, Luka; Gregorič, Asta; Zotter, Peter; Wolf, Robert; Bruns, Emily Anne; Prévôt, André S. H.; Petit, Jean-Eudes; Favez, Olivier; Sciare, Jean; Arnold, Ian J.; Chakrabarty, Rajan K.; Moosmüller, Hans; Filep, Agnes; Močnik, Griša

    2017-03-01

    Black carbon is a primary aerosol tracer for high-temperature combustion emissions and can be used to characterize the time evolution of its sources. It is correlated with a decrease in public health and contributes to atmospheric warming. Black carbon measurements are usually conducted with absorption filter photometers, which are prone to several artifacts, including the filter-loading effect - a saturation of the instrumental response due to the accumulation of the sample in the filter matrix. In this paper, we investigate the hypothesis that this filter-loading effect depends on the optical properties of particles present in the filter matrix, especially on the black carbon particle coating. We conducted field campaigns in contrasting environments to determine the influence of source characteristics, particle age and coating on the magnitude of the filter-loading effect. High-time-resolution measurements of the filter-loading parameter in filter absorption photometers show daily and seasonal variations of the effect. The variation is most pronounced in the near-infrared region, where the black carbon mass concentration is determined. During winter, the filter-loading parameter value increases with the absorption Ångström exponent. It is suggested that this effect is related to the size of the black carbon particle core as the wood burning (with higher values of the absorption Ångström exponent) produces soot particles with larger diameters. A reduction of the filter-loading effect is correlated with the availability of the coating material. As the coating of ambient aerosols is reduced or removed, the filter-loading parameter increases. Coatings composed of ammonium sulfate and secondary organics seem to be responsible for the variation of the loading effect. The potential source contribution function analysis shows that high values of the filter-loading parameter in the infrared are indicative of local pollution, whereas low values of the filter

  6. Primary and secondary contributions to aerosol light scattering and absorption in Mexico City during the MILAGRO 2006 campaign

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, G.; Arnott, W. P.; Jimenez, J. L.; Aiken, A. C.; Gaffney, J. S.; Marley, N. A.

    2009-06-01

    A photoacoustic spectrometer, a nephelometer, an aethalometer, and an aerosol mass spectrometer were used to measure at ground level real-time aerosol light absorption, scattering, and chemistry at an urban site located in North East Mexico City (Instituto Mexicano del Petroleo, Mexican Petroleum Institute, denoted by IMP), as part of the Megacity Impact on Regional and Global Environments field experiment, MILAGRO, in March 2006. Photoacoustic and reciprocal nephelometer measurements at 532 nm accomplished with a single instrument compare favorably with conventional measurements made with an aethalometer and a TSI nephelometer. The diurnally averaged single scattering albedo at 532 nm was found to vary from 0.60 to 0.85 with the peak value at midday and the minimum value at 07:00 a.m. local time, indicating that the Mexico City plume is likely to have a net warming effect on local climate. The peak value is associated with strong photochemical generation of secondary aerosol. It is estimated that the photochemical production of secondary aerosol (inorganic and organic) is approximately 75% of the aerosol mass concentration and light scattering in association with the peak single scattering albedo. A strong correlation of aerosol scattering at 532 nm and total aerosol mass concentration was found, and an average mass scattering efficiency factor of 3.8 m2/g was determined. Comparisons of photoacoustic and aethalometer light absorption with oxygenated organic aerosol concentration (OOA) indicate a very small systematic bias of the filter based measurement associated with OOA and the peak aerosol single scattering albedo.

  7. Primary and secondary contributions to aerosol light scattering and absorption in Mexico City during the MILAGRO 2006 campaign

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, G.; Arnott, W. P.; Jimenez, J. L.; Aiken, A. C.; Gaffney, J. S.; Marley, N. A.

    2008-09-01

    A photoacoustic spectrometer, a nephelometer, an aetholemeter, and an aerosol mass spectrometer were used to measure at ground level real-time aerosol light absorption, scattering, and chemistry at an urban site located in north east Mexico City (Instituto Mexicano del Petroleo, Mexican Petroleum Institute, denoted by IMP), as part of the Megacity Impact on Regional and Global Environments field experiment, MILAGRO, in March 2006. Photoacoustic and reciprocal nephelometer measurements at 532 nm accomplished with a single instrument compare favorably with conventional measurements made with an aethelometer and a TSI nephelometer. The diurnally averaged single scattering albedo at 532 nm was found to vary from 0.60 to 0.85 with the peak value at midday and the minimum value at 7 a.m. local time, indicating that the Mexico City plume is likely to have a net warming effect on local climate. The peak value is associated with strong photochemical generation of secondary aerosol. It is estimated that the same-day photochemical production of secondary aerosol (inorganic and organic) is approximately 40 percent of the aerosol mass concentration and light scattering in association with the peak single scattering albedo. A strong correlation of aerosol scattering at 532 nm and total aerosol mass concentration was found, and an average mass scattering efficiency factor of 3.8 m2/g was determined. Comparisons of photoacoustic and aethalometer light absorption with oxygenated organic aerosol concentration (OOA) indicate a very small systematic bias of the filter based measurement associated with OOA and the peak aerosol single scattering albedo.

  8. Optical properties and aging of light-absorbing secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; Laskin, Julia; Kathmann, Shawn M.; Wise, Matthew; Caylor, Ryan; Imholt, Felisha; Selimovic, Vanessa; Shilling, John E.

    2016-10-01

    The light-absorbing organic aerosol (OA) commonly referred to as "brown carbon" (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NOx concentrations, photolysis time, and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.

  9. In-Situ Measurements of Aerosol Optical Properties using New Cavity Ring-Down and Photoacoustics Instruments and Comparison with more Traditional Techniques

    NASA Technical Reports Server (NTRS)

    Strawa, A. W.; Arnott, P.; Covert, D.; Elleman, R.; Ferrare, R.; Hallar, A. G.; Jonsson, H.; Kirchstetter, T. W.; Luu, A. P.; Ogren, J.

    2004-01-01

    Carbonaceous species (BC and OC) are responsible for most of the absorption associated with aerosol particles. The amount of radiant energy an aerosol absorbs has profound effects on climate and air quality. It is ironic that aerosol absorption coefficient is one of the most difficult aerosol properties to measure. A new cavity ring-down (CRD) instrument, called Cadenza (NASA-ARC), measures the aerosol extinction coefficient for 675 nm and 1550 nm light, and simultaneously measures the scattering coefficient at 675 nm. Absorption coefficient is obtained from the difference of measured extinction and scattering within the instrument. Aerosol absorption coefficient is also measured by a photoacoustic (PA) instrument (DRI) that was operated on an aircraft for the first time during the DOE Aerosol Intensive Operating Period (IOP). This paper will report on measurements made with this new instrument and other in-situ instruments during two field recent field studies. The first field study was an airborne cam;oaign, the DOE Aerosol Intensive Operating Period flown in May, 2003 over northern Oklahoma. One of the main purposes of the IOP was to assess our ability to measure extinction and absorption coefficient in situ. This paper compares measurements of these aerosol optical properties made by the CRD, PA, nephelometer, and Particle Soot Absorption Photometer (PSAP) aboard the CIRPAS Twin-Otter. During the IOP, several significant aerosol layers were sampled aloft. These layers are identified in the remote (AATS-14) as well as in situ measurements. Extinction profiles measured by Cadenza are compared to those derived from the Ames Airborne Tracking Sunphotometer (AATS-14, NASA-ARC). The regional radiative impact of these layers is assessed by using the measured aerosol optical properties in a radiative transfer model. The second study was conducted in the Caldecott Tunnel, a heavily-used tunnel located north of San Francisco, Ca. The aerosol sampled in this study was

  10. Variability of aerosol optical properties derived from in situ aircraft measurements during ACE-Asia

    NASA Astrophysics Data System (ADS)

    Anderson, Theodore L.; Masonis, Sarah J.; Covert, David S.; Ahlquist, Norman C.; Howell, Steven G.; Clarke, Antony D.; McNaughton, Cameron S.

    2003-12-01

    Airborne measurements of aerosol light scattering (using nephelometers) and absorption (using particle/soot absorption photometers; PSAPs) in the Asian outflow region are presented. Aerosol particles were sampled through a new low turbulence inlet that proved very effective at transmitting coarse-mode particles. Noise and artifacts are characterized using in-flight measurements of particle-free air and measurements with identical instruments operated in parallel. For example, the sensitivities of PSAP noise to changing altitude, changing relative humidity (RH), and particle-loading on the internal filter are quantified. On the basis of these and previous instrument characterizations, we report averages, variations, and uncertainties of optical properties, focusing on data from approximately 300 level-leg samples obtained during 19 research flights in the spring of 2001. Several broad patterns emerge from this analysis. Two dominant components, fine-mode pollution and coarse-mode mineral dust, were observed to vary independently when separated using a cut point of 1 μm aerodynamic diameter at low RH. Fine-mode pollution was found to be moderately absorbing (single scatter albedo at low RH and 550 nm, ω = 0.88 ± 0.03; mean and 95% confidence uncertainty) and moderately hygroscopic (relative increase in scattering from 40% to 85% RH, fRH = 1.7 ± 0.2), while coarse-mode dust was found to have very low absorption (ω = 0.96 ± 0.01) and to be almost nonhygroscopic (fRH = 1.1 ± 0.1). These and other optical properties are intended to serve as constraints on optical models of the Asian aerosol for the purpose of satellite retrievals and calculations of direct radiative effects.

  11. Vertical Profiles of Cloud Condensation Nuclei, Condensation Nuclei, Optical Aerosol, Aerosol Optical Properties, and Aerosol Volatility Measured from Balloons

    NASA Technical Reports Server (NTRS)

    Deshler, T.; Snider, J. R.; Vali, G.

    1998-01-01

    Under the support of this grant a balloon-borne gondola containing a variety of aerosol instruments was developed and flown from Laramie, Wyoming, (41 deg N, 105 deg W) and from Lauder, New Zealand (45 deg S, 170 deg E). The gondola includes instruments to measure the concentrations of condensation nuclei (CN), cloud condensation nuclei (CCN), optically detectable aerosol (OA.) (r greater than or equal to 0.15 - 2.0 microns), and optical scattering properties using a nephelometer (lambda = 530 microns). All instruments sampled from a common inlet which was heated to 40 C on ascent and to 160 C on descent. Flights with the CN counter, OA counter, and nephelometer began in July 1994. The CCN counter was added in November 1994, and the engineering problems were solved by June 1995. Since then the flights have included all four instruments, and were completed in January 1998. Altogether there were 20 flights from Laramie, approximately 5 per year, and 2 from Lauder. Of these there were one or more engineering problems on 6 of the flights from Laramie, hence the data are somewhat limited on those 6 flights, while a complete data set was obtained from the other 14 flights. Good CCN data are available from 12 of the Laramie flights. The two flights from Lauder in January 1998 were successful for all measurements. The results from these flights, and the development of the balloon-bome CCN counter have formed the basis for five conference presentations. The heated and unheated CN and OA measurements have been used to estimate the mass fraction of the aerosol volatile, while comparisons of the nephelometer measurements were used to estimate the light scattering, associated with the volatile aerosol. These estimates were calculated for 0.5 km averages of the ascent and descent data between 2.5 km and the tropopause, near 11.5 km.

  12. Aerosols, light, and water: Measurements of aerosol optical properties at different relative humidities

    NASA Astrophysics Data System (ADS)

    Orozco, Daniel

    The Earth's atmosphere is composed of a large number of different gases as well as tiny suspended particles, both in solid and liquid state. These tiny particles, called atmospheric aerosols, have an immense impact on our health and on our global climate. Atmospheric aerosols influence the Earth's radiation budget both directly and indirectly. In the direct effect, aerosols scatter and absorb sunlight changing the radiative balance of the Earth-atmosphere system. Aerosols indirectly influence the Earth's radiation budget by modifying the microphysical and radiative properties of clouds as well as their water content and lifetime. In ambient conditions, aerosol particles experience hygroscopic growth due to the influence of relative humidity (RH), scattering more light than when the particles are dry. The quantitative knowledge of the RH effect and its influence on the light scattering coefficient and, in particular, on the phase function and polarization of aerosol particles is of substantial importance when comparing ground based observations with other optical aerosol measurements techniques such satellite and sunphotometric retrievals of aerosol optical depth and their inversions. This dissertation presents the aerosol hygroscopicity experiment investigated using a novel dryer-humidifier system, coupled to a TSI-3563 nephelometer, to obtain the light scattering coefficient (sp) as a function of relative humidity (RH) in hydration and dehydration modes. The measurements were performed in Porterville, CA (Jan 10-Feb 6, 2013), Baltimore, MD (Jul 3-30, 2013), and Golden, CO (Jul 12-Aug 10, 2014). Observations in Porterville and Golden were part of the NASA-sponsored DISCOVER-AQ project. The measured sp under varying RH in the three sites was combined with ground aerosol extinction, PM2:5mass concentrations, particle composition measurements, and compared with airborne observations performed during campaigns. The enhancement factor, f(RH), defined as the ratio of sp

  13. Aerosol Particle Property Comparisons Between MISR and AERONET Retrieved Values

    NASA Astrophysics Data System (ADS)

    Gaitley, B. J.; Kahn, R. A.

    2005-12-01

    Aerosol optical depth (AOT) data from the Multi-angle ImagingSpectroRadiometer (MISR) instrument aboard the NASA Earth Observing System's Terra satellite have already been systematically compared with ground-based data from the AERONET network. As a result of that study, MISR data are now being reprocessed with improved aerosol algorithms and aerosol models. The follow-on study reported here systematically compares MISR and AERONET particle micro-physical properties. This project is currently underway. Our goal is to use the statistical power of numerous AERONET measurements to map the behavior of the MISR property retrievals, identify strength and surprises in the MISR data, and use this information both to refine further the MISR retrieval algorithms and to assess the likely error envelopes in the MISR products. Multi-year data from 36 carefully chosen sites having good long-term measurement records are stratified by broad classes of aerosol air mass types: maritime, biomass burning, desert dust, pollution, and continental aerosols. Available AERONET spectral AOT measurements for two-hour windows around MISR overpass times are interpolated to MISR wavelengths and averaged, and AOT variability over the two-hour window is noted. Sky-scan AERONET data, taken only once an hour, are also were interpolated to MISR wavelengths, and are averaged over a four-hour window provided the variability is smaller than MISR sensitivity to particle properties based on previous work. MISR retrievals over the 17.6 km standard retrieval regions that include the AERONET sites are preferentially used for the comparison. The MISR measurements are averages of over all "successful" aerosol type models in the MISR algorithm climatology, where success is measured by the degree to which multi-angle, multi-spectral top-of-atmosphere radiances match modeled radiances, using several chi-squared tests. Angstrom exponent, single scattering albedo, and size distribution mean values and variance

  14. A COMPARISON OF CMAQ-BASED AEROSOL PROPERTIES WITH IMPROVE, MODIS, AND AERONET DATA

    EPA Science Inventory

    We compare select aerosol Properties derived from the Community Multiscale Air Quality (CMAQ) model-simulated aerosol mass concentrations with routine data from the National Aeronautics and Space Administration (NASA) satellite-borne Moderate Resolution Imaging Spectro-radiometer...

  15. Aerosol optical properties and mixing state of black carbon in the Pearl River Delta, China

    NASA Astrophysics Data System (ADS)

    Tan, Haobo; Liu, Li; Fan, Shaojia; Li, Fei; Yin, Yan; Cai, Mingfu; Chan, P. W.

    2016-04-01

    Aerosols contribute the largest uncertainty to the total radiative forcing estimate, and black carbon (BC) that absorbs solar radiation plays an important role in the Earth's energy budget. This study analysed the aerosol optical properties from 22 February to 18 March 2014 at the China Meteorological Administration Atmospheric Watch Network (CAWNET) station in the Pearl River Delta (PRD), China. The representative values of dry-state particle scattering coefficient (σsp), hemispheric backscattering coefficient (σhbsp), absorption coefficient (σabsp), extinction coefficient (σep), hemispheric backscattering fraction (HBF), single scattering albedo (SSA), as well as scattering Ångström exponent (α) were presented. A comparison between a polluted day and a clean day shows that the aerosol optical properties depend on particle number size distribution, weather conditions and evolution of the mixing layer. To investigate the mixing state of BC at the surface, an optical closure study of HBF between measurements and calculations based on a modified Mie model was employed for dry particles. The result shows that the mixing state of BC might be between the external mixture and the core-shell mixture. The average retrieved ratio of the externally mixed BC to the total BC mass concentration (rext-BC) was 0.58 ± 0.12, and the diurnal pattern of rext-BC can be found. Furthermore, considering that non-light-absorbing particles measured by a Volatility-Tandem Differential Mobility Analyser (V-TDMA) exist independently with core-shell and homogenously internally mixed BC particles, the calculated optical properties were just slightly different from those based on the assumption that BC exist in each particle. This would help understand the influence of the BC mixing state on aerosol optical properties and radiation budget in the PRD.

  16. Inferring brown carbon content from UV aerosol absorption measurements during biomass burning season

    NASA Astrophysics Data System (ADS)

    Mok, J.; Krotkov, N. A.; Arola, A. T.; Torres, O.; Jethva, H. T.; Andrade, M.; Labow, G. J.; Eck, T. F.; Li, Z.; Dickerson, R. R.; Stenchikov, G. L.; Osipov, S.

    2015-12-01

    Measuring spectral dependence of light absorption by colored organic or "brown" carbon (BrC) is important, because of its effects on photolysis rates of ozone and surface ultraviolet (UV) radiation. Enhanced UV spectral absorption by BrC can in turn be exploited for simultaneous retrievals of BrC and black carbon (BC) column amounts in field campaigns. We present an innovative ground-based retrieval of BC and BrC volume fractions and their mass absorption efficiencies during the biomass burning season in Santa Cruz, Bolivia in September-October 2007. Our method combines retrieval of BC volume fraction using AERONET inversion in visible wavelengths with the inversion of total BC+BrC absorption (i.e., column effective imaginary refractive index, kmeas) using Diffuse/Direct irradiance measurements in UV wavelengths. First, we retrieve BrC volume fraction by fitting kmeas at 368nm using Maxwell-Garnett (MG) mixing rules assuming: (1) flat spectral dependence of kBC, (2) known value of kBrC at 368nm from laboratory absorption measurements or smoke chamber experiments, and (3) known BC volume fraction from AERONET inversion. Next, we derive kBrC in short UVB wavelengths by fitting kmeas at 305nm, 311nm, 317nm, 325nm, and 332nm using MG mixing rules and fixed volume fractions of BC and BrC. Our retrievals show larger than expected spectral dependence of kBrC in UVB wavelengths, implying reduced surface UVB irradiance and inhibited photolysis rates of surface ozone destruction. We use a one-dimensional chemical box model to show that the observed strong wavelength dependence of BrC absorption leads to inhibited photolysis of ozone to O(1D), a loss mechanism, while having little impact or even accelerating photolysis of NO2, an ozone production mechanism. Although BC only absorption in biomass burning aerosols is important for climate radiative forcing in the visible wavelengths, additional absorption by BrC is important because of its impact on surface UVB radiation

  17. Effective absorption cross sections and photolysis rates of anthropogenic and biogenic secondary organic aerosols

    NASA Astrophysics Data System (ADS)

    Romonosky, Dian E.; Ali, Nujhat N.; Saiduddin, Mariyah N.; Wu, Michael; Lee, Hyun Ji (Julie); Aiona, Paige K.; Nizkorodov, Sergey A.

    2016-04-01

    Mass absorption coefficient (MAC) values were measured for secondary organic aerosol (SOA) samples produced by flow tube ozonolysis and smog chamber photooxidation of a wide range of volatile organic compounds (VOC), specifically: α-pinene, β-pinene, β-myrcene, d-limonene, farnesene, guaiacol, imidazole, isoprene, linalool, ocimene, p-xylene, 1-methylpyrrole, and 2-methylpyrrole. Both low-NOx and high-NOx conditions were employed during the chamber photooxidation experiments. MAC values were converted into effective molecular absorption cross sections assuming an average molecular weight of 300 g/mol for SOA compounds. The upper limits for the effective photolysis rates of SOA compounds were calculated by assuming unity photolysis quantum yields and convoluting the absorption cross sections with a time-dependent solar spectral flux. A more realistic estimate for the photolysis rates relying on the quantum yield of acetone was also obtained. The results show that condensed-phase photolysis of SOA compounds can potentially occur with effective lifetimes ranging from minutes to days, suggesting that photolysis is an efficient and largely overlooked mechanism of SOA aging.

  18. Relationship between aerosol oxidation level and hygroscopic properties of laboratory generated secondary organic aerosol (SOA) particles

    NASA Astrophysics Data System (ADS)

    Massoli, P.; Lambe, A.; Ahern, A.; Williams, L. R.; Ehn, M.; Mikkila, J.; Canagaratna, M.; Brune, W. H.; Onasch, T. B.; Jayne, J.; Petdjd, T. T.; Kulmala, M. T.; Laaksonen, A.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R.

    2010-12-01

    Laboratory experiments investigated the relationship between degree of oxidation and hygroscopic properties of secondary organic aerosol (SOA) particles. The hygroscopic growth factor (HGF), the CCN activity (κCCN) and the degree of aerosol oxidation (represented by the atomic O:C ratio) were measured for α-pinene, 1,3,5-trimethylbenzene (TMB), m-xylene and α pinene/m-xylene mixture SOA generated via OH radical oxidation in an aerosol flow reactor. Our results show that both HGF and κCCN increase with O:C. The TMB and m-xylene SOA were, respectively, the least and most hygroscopic of the system studied. An average HGF of 1.25 and a κCCN of 0.2 were measured at O:C of 0.65, in agreement with results reported for ambient data. The HGF based κ(κHGF) under predicted the κCCN values of 20 to 50% for all but the TMB SOA. Within the limitations of instrumental capabilities, we define the extent to which the hygroscopic properties of SOA particles can be predicted from their oxidation level and provide parameterizations suitable for interpreting ambient data.

  19. Biomass burning aerosol over the Amazon during SAMBBA: impact of chemical composition on radiative properties

    NASA Astrophysics Data System (ADS)

    Morgan, William; Allan, James; Flynn, Michael; Darbyshire, Eoghan; Hodgson, Amy; Liu, Dantong; O'shea, Sebastian; Bauguitte, Stephane; Szpek, Kate; Langridge, Justin; Johnson, Ben; Haywood, Jim; Longo, Karla; Artaxo, Paulo; Coe, Hugh

    2014-05-01

    Biomass burning represents one of the largest sources of particulate matter to the atmosphere, resulting in a significant perturbation to the Earth's radiative balance coupled with serious impacts on public health. Globally, biomass burning aerosols are thought to exert a small warming effect but with the uncertainty being 4 times greater than the central estimate. On regional scales, the impact is substantially greater, particularly in areas such as the Amazon Basin where large, intense and frequent burning occurs on an annual basis for several months. Absorption by atmospheric aerosols is underestimated by models over South America, which points to significant uncertainties relating to Black Carbon (BC) aerosol properties. Initial results from the South American Biomass Burning Analysis (SAMBBA) field experiment, which took place during September and October 2012 over Brazil on-board the UK Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft, are presented here. Aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) and a DMT Single Particle Soot Photometer (SP2). The physical, chemical and optical properties of the aerosols across the region will be characterized in order to establish the impact of biomass burning on regional air quality, weather and climate. The aircraft sampled a range of conditions including sampling of pristine Rainforest, fresh biomass burning plumes, regional haze and elevated biomass burning layers within the free troposphere. The aircraft sampled biomass burning aerosol across the southern Amazon in the states of Rondonia and Mato Grosso, as well as in a Cerrado (Savannah-like) region in Tocantins state. This presented a range of fire conditions, both in terms of their number, intensity, vegetation-type and their combustion efficiencies. Near-source sampling of fires in Rainforest environments suggested that smouldering combustion dominated, while flaming combustion dominated

  20. Evaluations of tropospheric aerosol properties simulated by the community earth system model with a sectional aerosol microphysics scheme.

    PubMed

    Yu, Pengfei; Toon, Owen B; Bardeen, Charles G; Mills, Michael J; Fan, Tianyi; English, Jason M; Neely, Ryan R

    2015-06-01

    A sectional aerosol model (CARMA) has been developed and coupled with the Community Earth System Model (CESM1). Aerosol microphysics, radiative properties, and interactions with clouds are simulated in the size-resolving model. The model described here uses 20 particle size bins for each aerosol component including freshly nucleated sulfate particles, as well as mixed particles containing sulfate, primary organics, black carbon, dust, and sea salt. The model also includes five types of bulk secondary organic aerosols with four volatility bins. The overall cost of CESM1-CARMA is approximately ∼2.6 times as much computer time as the standard three-mode aerosol model in CESM1 (CESM1-MAM3) and twice as much computer time as the seven-mode aerosol model in CESM1 (CESM1-MAM7) using similar gas phase chemistry codes. Aerosol spatial-temporal distributions are simulated and compared with a large set of observations from satellites, ground-based measurements, and airborne field campaigns. Simulated annual average aerosol optical depths are lower than MODIS/MISR satellite observations and AERONET observations by ∼32%. This difference is within the uncertainty of the satellite observations. CESM1/CARMA reproduces sulfate aerosol mass within 8%, organic aerosol mass within 20%, and black carbon aerosol mass within 50% compared with a multiyear average of the IMPROVE/EPA data over United States, but differences vary considerably at individual locations. Other data sets show similar levels of comparison with model simulations. The model suggests that in addition to sulfate, organic aerosols also significantly contribute to aerosol mass in the tropical UTLS, which is consistent with limited data.

  1. Evaluation of aerosol properties simulated by the high resolution global coupled chemistry-aerosol-microphysics model C-IFS-GLOMAP

    NASA Astrophysics Data System (ADS)

    Dhomse, Sandip; Mann, Graham; Carslaw, Ken; Flemming, Johannes; Morcrette, Jean-Jacques; Engelen, Richard; Remy, Samuel; Boucher, Olivier; Benduhn, Francois; Hewson, Will; Woodhouse, Matthew

    2016-04-01

    The EU Framework Programme GEMS and MACC consortium projects co-ordinated by the European Centre for Medium-range Weather Forecasts (ECMWF) have developed an operational global forecasting and reanalysis system (Composition-IFS) for atmospheric composition including greenhouse gases, reactive gases and aerosol. The current operational C-IFS system uses a mass-based aerosol model coupled to data assimilation of Aerosol Optical Depth measured by satellite (MODIS) to predict global aerosol properties. During MACC, the GLOMAP-mode aerosol microphysics scheme was added to the system, providing information on aerosol size and number for improved representation of aerosol-radiation and aerosol-cloud interactions, accounting also for simulated global variations in size distribution and internally-mixed particle composition. The IFS-GLOMAP system has recently been upgraded to couple with the sulphur cycle simulated in the online TM5 tropospheric chemistry module for global reactive gases. This C-IFS-GLOMAP system is also being upgraded to use a new "nitrate-extended" version of GLOMAP which realistically treats the size-resolved gas-particle partitioning of semi volatile gases ammonia and nitric acid. In this poster we described C-IFS-GLOMAP and present an evaluation of the global sulphate aerosol distribution simulated in this coupled aerosol-chemistry C-IFS-GLOMAP, comparing to surface observations in Europe, North America and the North Atlantic and contrasting to the fixed timescale sulphate production scheme developed in GEMS. We show that the coupling to the TM5 sulphur chemistry improves the seasonal cycle of sulphate aerosol, for example addressing a persistent wintertime sulphate high bias in northern Europe. The improved skill in simulated sulphate aerosol seasonal cycle is a pre-requisite to realistically characterise nitrate aerosol since biases in sulphate affect the amount of free ammonia available to form ammonium nitrate.

  2. Evaluations of tropospheric aerosol properties simulated by the community earth system model with a sectional aerosol microphysics scheme

    PubMed Central

    Toon, Owen B.; Bardeen, Charles G.; Mills, Michael J.; Fan, Tianyi; English, Jason M.; Neely, Ryan R.

    2015-01-01

    Abstract A sectional aerosol model (CARMA) has been developed and coupled with the Community Earth System Model (CESM1). Aerosol microphysics, radiative properties, and interactions with clouds are simulated in the size‐resolving model. The model described here uses 20 particle size bins for each aerosol component including freshly nucleated sulfate particles, as well as mixed particles containing sulfate, primary organics, black carbon, dust, and sea salt. The model also includes five types of bulk secondary organic aerosols with four volatility bins. The overall cost of CESM1‐CARMA is approximately ∼2.6 times as much computer time as the standard three‐mode aerosol model in CESM1 (CESM1‐MAM3) and twice as much computer time as the seven‐mode aerosol model in CESM1 (CESM1‐MAM7) using similar gas phase chemistry codes. Aerosol spatial‐temporal distributions are simulated and compared with a large set of observations from satellites, ground‐based measurements, and airborne field campaigns. Simulated annual average aerosol optical depths are lower than MODIS/MISR satellite observations and AERONET observations by ∼32%. This difference is within the uncertainty of the satellite observations. CESM1/CARMA reproduces sulfate aerosol mass within 8%, organic aerosol mass within 20%, and black carbon aerosol mass within 50% compared with a multiyear average of the IMPROVE/EPA data over United States, but differences vary considerably at individual locations. Other data sets show similar levels of comparison with model simulations. The model suggests that in addition to sulfate, organic aerosols also significantly contribute to aerosol mass in the tropical UTLS, which is consistent with limited data. PMID:27668039

  3. Photoacoustic and filter-based ambient aerosol light absorption measurements: Instrument comparisons and the role of relative humidity

    NASA Astrophysics Data System (ADS)

    Arnott, W. P.; Moosmüller, H.; Sheridan, P. J.; Ogren, J. A.; Raspet, R.; Slaton, W. V.; Hand, J. L.; Kreidenweis, S. M.; Collett, J. L.

    2003-01-01

    Ambient measurements are reported of aerosol light absorption from photoacoustic and filter-based instruments (aethalometer and a particle soot absorption photometer (PSAP)) to provide insight on the measurement science. Measurements were obtained during the Big Bend Regional Aerosol and Visibility Observational Study at the Big Bend National Park in South Texas. The aethalometer measurements of black carbon concentration at this site correlate reasonably well with photoacoustic measurements of aerosol light absorption, with a slope of 8.1 m2/g and a small offset. Light absorption at this site never exceeded 2.1 Mm-1 during the month of collocated measurements. Measurements were also obtained, as a function of controlled relative humidity between 40% and 90%, during the Photoacoustic IOP in 2000 at the Department of Energy Southern Great Plains Cloud and Radiation Testbed site (SGP). PSAP measurements of aerosol light absorption correlated very well with photoacoustic measurements, but the slope of the correlation indicated the PSAP values were larger by a factor of 1.61. The photoacoustic measurements of light absorption exhibited a systematic decrease when the RH increased beyond 70%. This apparent decrease in light absorption with RH may be due to the contribution of mass transfer to the photoacoustic signal. Model results for the limiting case of full water saturation are used to evaluate this hypothesis. A second PSAP measured the light absorption for the same humidified samples, and indicated very erratic response as the RH changed, suggesting caution when interpreting PSAP data under conditions of rapid relative humidity change.

  4. Aerosol optical properties at a coastal site in Hong Kong, South China: temporal features, size dependencies and source analysis

    NASA Astrophysics Data System (ADS)

    Wang, Jiaping; Ding, Aijun; Virkkula, Aki; Lee, Shuncheng; Shen, Yicheng; Chi, Xuguang; Xu, Zheng

    2016-04-01

    Hong Kong is a typical coastal city adjacent to the Pearl River Delta (PRD) region in southern China, which is one of the regions suffering from severe air pollution. Atmospheric aerosols can affect the earth's radiative balance by scattering and absorbing incoming solar radiation. Black Carbon (BC) aerosol is a particularly emphasized component due to its strong light absorption. Aerosol transported from different source areas consists of distinct size distributions, leading to different optical properties. As the byproducts of the incomplete oxidation, BC and CO both have relatively long life time, their relationship is a good indicator for distinguishing different pollutant sources. In this study, temporal variations of aerosol optical properties and concentrations of BC and CO at a coastal background station in Hong Kong were investigated. Transport characteristics and origins of aerosol were elucidated by analyzing backward Lagrangian particle dispersion modeling (LPDM) results, together with related parameters including the relationships between optical properties and particle size, BC-CO correlations, ship location data and meteorological variables. From February 2012 to September 2013 and March 2014 to February 2015, continuous in-situ measurements of light scattering and absorption coefficients, particle size distribution and concentrations of BC and CO were conducted at Hok Tsui (HT), a coastal background station on the southeast tip of Hong Kong Island (22.22°N, 114.25°E, 60 m above the sea level) with few local anthropogenic activities. Affected by the Asian monsoon, this region is dominated by continental outflow in winter and by marine inflow from the South China Sea in summer, which is an ideal station for identifying the transport characteristics of aerosol and their effects on optical properties from different anthropogenic emission sources. 7-day backward Lagrangian particle dispersion modeling was performed for source identification. Three

  5. Sensitivity of thermal infrared sounders to the chemical and micro-physical properties of UTLS secondary sulphate aerosols

    NASA Astrophysics Data System (ADS)

    Sellitto, P.; Legras, B.

    2015-08-01

    Monitoring upper tropospheric-lower stratospheric (UTLS) secondary sulphate aerosols and their chemical and micro-physical properties from satellite nadir observations is crucial to better understand their formation and evolution processes and then to estimate their impact to the UTLS chemistry, and on regional and global radiative balance. Here we present a study aimed at the evaluation of the sensitivity of thermal infrared (TIR) satellite nadir observations to the chemical composition and the size distribution of idealized UTLS sulphate aerosol layers. The extinction properties of sulphuric acid/water droplets, for different sulphuric acid mixing ratios and temperatures, are systematically analysed. The extinction coefficients are derived by means of a Mie code, using refractive indexes taken from the GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques: Management and Study of Spectroscopic Information) spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer) pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model, to estimate the impact of the extinction of idealized aerosol layers, at typical UTLS conditions, on the brightness temperature spectra observed by this satellite instrument. We found a marked and typical spectral signature of these aerosol layers between 700 and 1200 cm-1, due to the absorption bands of the sulphate and bi-sulphate ions and the undissociated sulphuric acid, with the main absorption peaks at 1170 and 905 cm-1. The dependence of the aerosol spectral signature to the sulphuric acid mixing ratio, and effective number concentration and radius, as well as the role of interferring parameters like the ozone, sulphur dioxide, carbon dioxide and ash absorption, and temperature and water vapour profile

  6. Aerosols

    Atmospheric Science Data Center

    2013-04-17

    ... article title:  Aerosols over Central and Eastern Europe     View Larger Image ... last weeks of March 2003, widespread aerosol pollution over Europe was detected by several satellite-borne instruments. The Multi-angle ...

  7. Contribution of long-range transported aerosols to aerosol optical and physical properties: 3-year measurements at Gosan, Korea

    NASA Astrophysics Data System (ADS)

    Heo, J.; Kim, S. W.; Kim, J. H.; Ogren, J. A.; Yoon, S. C.

    2015-12-01

    Recently, more attentions have been paid to air quality in East Asia due to the enhanced loading of atmospheric pollutants related to rapid industrialization. Gosan Climate Observatory (GCO), Korea is regarded as an ideal site to study the transport of atmospheric pollutants because it is frequently influenced by various airmasses from China, Korea, Japan and Pacific Ocean. In order to understand aerosol optical and physical properties according to airmass transport routes, three-year (2012-2014) continuous measurements of aerosol scattering/absorption coefficient and number size distribution were analyzed, together with 48-hour backward trajectory calculations. The averaged aerosol absorption (σa) and scattering coefficient (σs) for airmasses transported from North China (NC; 36% of all trajectories) were 6.65 Mm-1 and 94.72 Mm-1 at 550 nm wavelength, respectively, which were similar to those for stagnant airmasses (ST; 22% of all trajectories; σa: 6.26 Mm-1, σs: 93.99 Mm-1). The highest values of σa (7.03 Mm-1) and σs (108.34 Mm-1) were observed when airmasses were traveled from South China (SC; 11% of all trajectories). σa and σs for airmasses from Korean Peninsula (KP; 7% of all trajectories) and Pacific Ocean (PO; 14% of all trajectories; in parenthesis) were 5.63 (2.76) Mm-1 and 73.63 (50.93) Mm-1, respectively. Compared to other airmasses, the higher values of Scattering Angstrom Exponent (SAE) for ST (1.65) is thought to be the build-up of anthropogenic fine particulate pollutants. The Absorption Angstrom Exponent (AAE) was estimated to be 1.32 for NC airmass and 1.02 for SC airmass. Over the study period, 130 days of total 557 days were identified as new particle formation and growth event (NPF) from Scanning Mobility Particle Sizer (SMPS) measurements by Cyclostationary Empirical Orthogonal Function (CSEOF) approach. Especially, 55.4% (72 days) of total 130 NPF days were found when a cold and dry airmass comes from NC after passing the frontal

  8. Optical properties and cross-sections of biological aerosols

    NASA Astrophysics Data System (ADS)

    Thrush, E.; Brown, D. M.; Salciccioli, N.; Gomes, J.; Brown, A.; Siegrist, K.; Thomas, M. E.; Boggs, N. T.; Carter, C. C.

    2010-04-01

    There is an urgent need to develop standoff sensing of biological agents in aerosolized clouds. In support of the Joint Biological Standoff Detection System (JBSDS) program, lidar systems have been a dominant technology and have shown significant capability in field tests conducted in the Joint Ambient Breeze Tunnel (JABT) at Dugway Proving Ground (DPG). The release of biological agents in the open air is forbidden. Therefore, indirect methods must be developed to determine agent cross-sections in order to validate sensor against biological agents. A method has been developed that begins with laboratory measurements of thin films and liquid suspensions of biological material to obtain the complex index of refraction from the ultraviolet (UV) to the long wave infrared (LWIR). Using that result and the aerosols' particle size distribution as inputs to Mie calculations yields the backscatter and extinction cross-sections as a function of wavelength. Recent efforts to model field measurements from the UV to the IR have been successful. Measurements with aerodynamic and geometric particle sizers show evidence of particle clustering. Backscatter simulations of these aerosols show these clustered particles dominate the aerosol backscatter and depolarization signals. In addition, these large particles create spectral signatures in the backscatter signal due to material absorption. Spectral signatures from the UV to the IR have been observed in simulations of field releases. This method has been demonstrated for a variety of biological simulant materials such as Ovalbumin (OV), Erwinia (EH), Bacillus atrophaeus (BG) and male specific bacteriophage (MS2). These spectral signatures may offer new methods for biological discrimination for both stand-off sensing and point detection systems.

  9. Sources and light absorption of water-soluble organic carbon aerosols in the outflow from northern China

    NASA Astrophysics Data System (ADS)

    Kirillova, E. N.; Andersson, A.; Han, J.; Lee, M.; Gustafsson, Ö.

    2014-02-01

    High loadings of anthropogenic carbonaceous aerosols in Chinese air influence the air quality for over one billion people and impact the regional climate. A large fraction (17-80%) of this aerosol carbon is water-soluble, promoting cloud formation and thus climate cooling. Recent findings, however, suggest that water-soluble carbonaceous aerosols also absorb sunlight, bringing additional direct and indirect climate warming effects, yet the extent and nature of light absorption by this water-soluble "brown carbon" and its relation to sources is poorly understood. Here, we combine source estimates constrained by dual carbon isotopes with light-absorption measurements of water-soluble organic carbon (WSOC) for a March 2011 campaign at the Korea Climate Observatory at Gosan (KCOG), a receptor station in SE Yellow Sea for the outflow from northern China. The mass absorption cross section at 365 nm (MAC365) of WSOC for air masses from N. China were in general higher (0.8-1.1 m2 g-1), than from other source regions (0.3-0.8 m2 g-1). However, this effect corresponds to only 2-10% of the radiative forcing caused by light absorption by elemental carbon. Radiocarbon constraints show that the WSOC in Chinese outflow had significantly higher fraction fossil sources (30-50%) compared to previous findings in S. Asia, N. America and Europe. Stable carbon (δ13C) measurements were consistent with aging during long-range air mass transport for this large fraction of carbonaceous aerosols.

  10. Environmental temperature effect on the far-infrared absorption features of aromatic-based Titan's aerosol analogs

    NASA Astrophysics Data System (ADS)

    Gautier, Thomas; Trainer, Melissa G.; Loeffler, Mark J.; Sebree, Joshua A.; Anderson, Carrie M.

    2017-01-01

    Benzene detection has been reported in Titan's atmosphere both in the stratosphere at ppb levels by remote sensing (Coustenis et al., 2007; Vinatier et al., 2007) and in the thermosphere at ppm levels by the Cassini's Ion and Neutral Mass Spectrometer (Waite et al., 2007). This detection supports the idea that aromatic and heteroaromatic reaction pathways may play an important role in Titan's atmospheric chemistry, especially in the formation of aerosols. Indeed, aromatic molecules are easily dissociated by ultraviolet radiation and can therefore contribute significantly to aerosol formation. It has been shown recently that aerosol analogs produced from a gas mixture containing a low concentration of aromatic and/or heteroaromatic molecules (benzene, naphthalene, pyridine, quinoline and isoquinoline) have spectral signatures below 500 cm-1, a first step towards reproducing the aerosol spectral features observed by Cassini's Composite InfraRed Spectrometer (CIRS) in the far infrared (Anderson and Samuelson 2011, and references therein). In this work we investigate the influence of environmental temperature on the absorption spectra of such aerosol samples, simulating the temperature range to which aerosols, once formed, are exposed during their transport through Titan's stratosphere. Our results show that environmental temperature does not have any major effect on the spectral shape of these aerosol analogs in the far-infrared, which is consistent with the CIRS observations.

  11. Studing Taklamakan aerosol properties with Lidar (STAPL)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    By now, the global impacts of atmospheric dust have been well-established. Nevertheless, relevant properties such as size distribution, depolarization ratio, and even single-scattering albedo have been shown to vary substantially between dust producing regions and are also strongly dependent on the ...

  12. Aerosol light absorption measurements during the Reno Aerosol Optics Experiment: Photoacoustic measurements and a multiple-scattering model for the aethalometer response.

    NASA Astrophysics Data System (ADS)

    Arnott, W. P.; Moosmueller, H.; Sheridan, P. J.; Ogren, J. A.

    2002-12-01

    The filter used on the aethalometer is a multiple scattering substrate, yet the current parameterization of the instrument simply uses Beer's law for its analysis when obtaining black carbon concentration. Specific characterizations of the instrument response, where filter attenuation was obtained as a function of wavelength, gave the following impressions. 1. Filter attenuation generally increases inversely with wavelength for all aerosol types. 2. When subjected to a constant flow of low single scattering albedo aerosol, the instrument shows a non-constant response. The response is highest when the filter single scattering albdeo is highest, and it decreases as the filter blackens. 3. When subjected to a constant flow of essentially unity single scattering albedo aerosol, the instrument shows a non-zero response, even though it should do so. A few percent of scattering is converted to absorption, because the addition of purely scattering aerosol is analogous to a simple thickening of the filter. The effect is more pronounced at shorter wavelengths, and is related to item 1. The multiple scattering model reproduces these behaviors. The photoacoustic instrument light absorption calibration with nitrogen dioxide gas will be presented along with closure data from extinction minus scattering as evaluations of its measurement accuracy.

  13. Analysis of the sensitivity of thermal infrared nadir satellite observations to the chemical and micro-physical properties of upper tropospheric-lower stratospheric sulphate aerosols

    NASA Astrophysics Data System (ADS)

    Sellitto, Pasquale; Sèze, Geneviève; Legras, Bernard

    2015-04-01

    Secondary sulphate aerosols are the predominant typology of aerosols in the upper troposphere/lower stratosphere (UTLS), and can have an important impact on radiative transfer and climate, cirrus formation and chemistry in the UTLS. Despite their importance, the satellite observation at the regional scale of sulphate aerosols in the UTLS is limited. In this work, we address the sensitivity of the thermal infrared satellite observations to secondary sulphate aerosols in the UTLS. The absorption properties of sulphuric acid/water droplets, for different sulphuric acid mixing ratios and temperatures, are systematically analysed. The absorption coefficients are derived by means of a Mie code, using refractive indexes taken from the GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques : Management and Study of Spectroscopic Information) spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer) and SEVIRI (Spinning Enhanced Visible and Infrared Imager) pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model, to estimate the impact of the absorption of idealized aerosol layers, at typical UTLS conditions, on the radiance spectra observed by these simulated satellite instruments. We found a marked spectral signature of these aerosol layers between 700 and 1200 cm-1, due to the absorption bands of the sulphate and bi-sulphate ions and the undissociated sulphuric acid, with absorption peaks at 1170 and 905 cm-1. Micro-windows with a sensitivity to chemical and micro-physical properties of the sulphate aerosol layer are identified, and the role of interfering species, and temperature and water vapour profile is discussed.

  14. A three-dimensional sectional representation of aerosol mixing state for simulating optical properties and cloud condensation nuclei

    SciTech Connect

    Ching, Ping Pui; Zaveri, Rahul A.; Easter, Richard C.; Riemer, Nicole; Fast, Jerome D.

    2016-05-27

    Light absorption by black carbon (BC) particles emitted from fossil fuel combustion depends on the how thickly they are coated with non-refractory species such as ammonium, sulfate, nitrate, organics, and water. The cloud condensation nuclei (CCN) activation property of a particle depends on its dry size and the hygroscopicities of all the individual species mixed together. It is therefore necessary to represent both size and mixing state of aerosols to reliably predict their climate-relevant properties in atmospheric models. Here we describe and evaluate a novel sectional framework in the Model for Simulating Aerosol Interactions and Chemistry, referred to as MOSAIC-mix, that represents the mixing state by resolving aerosol dry size (Ddry), BC dry mass fraction (wBC), and hygroscopicity (κ). Using ten idealized urban plume scenarios in which different types of aerosols evolve over 24 hours under a range of atmospherically relevant environmental conditions, we examine errors in CCN concentrations and optical properties with respect to a more explicit aerosol mixing state representation. We find that only a small number of wBC and κ bins are needed to achieve significant reductions in the errors, and propose a configuration consisting of 24 Ddry bins, 2 wBC bins, and 2 κ bins that gives 24-hour average errors of about 5% or less in CCN concentrations and optical properties, 3-4 times lower than those from size-only-resolved simulations. These results show that MOSAIC-mix is suitable for use in regional and global models to examine the effects of evolving aerosol mixing states on aerosol-radiation-cloud feedbacks.

  15. Impact of North American intense fires on aerosol optical properties measured over the European Arctic in July 2015

    NASA Astrophysics Data System (ADS)

    Markowicz, K. M.; Pakszys, P.; Ritter, C.; Zielinski, T.; Udisti, R.; Cappelletti, D.; Mazzola, M.; Shiobara, M.; Xian, P.; Zawadzka, O.; Lisok, J.; Petelski, T.; Makuch, P.; Karasiński, G.

    2016-12-01

    In this paper impact of intensive biomass burning (BB) in North America in July 2015, on aerosol optical and microphysical properties measured in the European Arctic, is discussed. This study was made within the framework of the Impact of Absorbing aerosols on Radiating forcing in the European Arctic project. During the BB event aerosol optical depth (AOD) at 500 nm exceeded 1.2 in Spitsbergen and 0.7 in Andenes (Norway). Angstrom exponent exceeded 1.4, while the absorbing Angstrom exponent varied between 1 and 1.25. BB aerosols were observed in humid atmosphere with a total water vapor column between 2 and 2.5 cm. In such conditions aerosols are activated and may produce clouds at different altitudes. Vertical structure of aerosol plumes over Svalbard, obtained from ceilometers and lidars, shows variability of range-corrected signal between surface and middle and upper troposphere. Aerosol backscattering coefficients show values up to 10-5 m-1 sr-1 at 532 nm. Aerosol surface observations indicate chemical composition typical for biomass burning particles and very high single scattering properties. Scattering and absorption coefficients at 530 nm were up to 130 and 15 Mm-1, respectively. Single scattering albedo at the surface varied from 0.9 to 0.94. The averaged values over the entire atmospheric column ranged from 0.93 to 0.99. Preliminary statistics of model and Sun photometer data as well as previous studies indicate that this event, in the Arctic region, must be considered extreme (such AOD was not observed in Svalbard since 2005) with a significant impact on energy budget.

  16. In Situ Measurements of Aerosol Mass Concentration and Spectral Absorption at Three Location in and Around Mexico City

    NASA Astrophysics Data System (ADS)

    Chaudhry, Z.; Martins, V.; Li, Z.

    2006-12-01

    As a result of population growth and increasing industrialization, air pollution in heavily populated urban areas is one of the central environmental problems of the century. As a part of the MILAGRO (Megacity Initiative: Local and Global Research Observations) study, Nuclepore filters were collected in two size ranges (PM10 and PM2.5) at 12 hour intervals at three location in Mexico during March, 2006. Sampling stations were located at the Instituto Mexicano del Petroleo (T0), at the Rancho La Bisnago in the State of Hidalgo (T2) and along the Gulf Coast in Tampico (Tam). Each filter was analyzed for mass concentration, aerosol scattering and absorption efficiencies. Mass concentrations at T0 ranged from 47 to 179 μg/m3 for PM10 with an average concentration of 96 μg/m3, and from 20 to 93 μg/m3 for PM2.5 with an average concentration of 41 μg/m3. Mass concentrations at T2 ranged from 12 to 154 μg/m3 for PM10 with an average concentration of 51 μg/m3, and from 7 to 50 μg/m3 for PM2.5 with an average concentration of 25 μg/m3. Mass concentrations at Tam ranged from 34 to 80 μg/m3 for PM10 with an average concentration of 52 μg/m3, and from 8 to 23 μg/m3 for PM2.5 with an average concentration of 13 μg/m3. While some of the extreme values are likely linked to local emissions, regional air pollution episodes also played important roles. Each of the sampling stations experienced a unique atmospheric condition. The site at T0 was influenced by urban air pollution and dust storms, the site at T2 was significantly less affected by air pollution but more affected by regional dust storms and local dust devils while Tam was influenced by air pollution, dust storms and the natural marine environment. The spectral mass absorption efficiency was measured from 350 to 2500 nm and shows large differences between the absorption properties of soil dust, black carbon, and organic aerosols. The strong spectral differences observed can be related to differences in

  17. Optical properties of aerosols in Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Skorov, Yu. V.; Keller, H. U.; Rodin, A. V.

    2008-04-01

    In the frame of fractal modeling of tholin aggregates we made a systematic analysis of their optical properties. Ballistic particle-cluster aggregation (BPCA) and diffusion-limited aggregation (DLA) of spherical primary particles (monomers) identical in material composition were considered. Aggregates composed of identical particles (monodisperse cluster), as well as of size-distributed particles (polydisperse cluster), were simulated. To calculate the light-scattering models, the code based on the superposition T-matrix method is used. Orientationally averaged properties of light scattering by model particles were extracted, and the normalized phase function and the degree of linear polarization were calculated as functions of scattering angle. We concluded that: (a) aggregation mechanism as well as specific internal structure of the clusters play only a minor role, and for the future it is not necessary to investigate aggregates of different types; (b) the intensity is very sensitive both to the size parameter of forming particles x and to the size parameter of the aggregates X; (c) characterization of the aggregates by the number of monomers is insufficient to retrieve physical properties of aggregates from optical measurement; and (d) it is very desirable to include into the analysis polarization data calculated for the different clusters.

  18. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2016-02-01

    This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June-July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of transport (1-5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried a higher concentration of pollution particles below 3 km above sea level (a.s.l.) than above 3 km a.s.l., resulting in a scattering Ångström exponent up to 2.2 below 3 km a.s.l. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate absorption of light by the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assumed similar to those of native dust in radiative transfer simulations, modelling studies and satellite retrievals

  19. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2015-08-01

    This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June-July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of tranport (1-5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried higher concentration of pollution particles at intermediate altitude (1-3 km) than at elevated altitude (> 3 km), resulting in scattering Angstrom exponent up to 2.2 within the intermediate altitude. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate light absorption of the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00 ± 0.04. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assimilated to those of native dust in radiative transfer simulations, modeling studies and

  20. Evaluation of Aerosol Properties in GCMs using Satellite Measurements

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Jiang, J. H.; Su, H.; Zhang, H.

    2015-12-01

    Atmospheric aerosols from natural or anthropogenic sources have profound impacts on the regional and global climate. Currently the radiative forcing of aerosols predicted by global climate models remains highly uncertain, representing the largest uncertainty in climate predictions. The uncertainty mainly arises from the complicated aerosol chemical and physical properties, coarse emission inventories for pre-cursor gases as well as unrealistic representations of aerosol activation and cloud processing in global climate models. In this study, we will utilize multiple satellite measurements including MODIS, MISR and CALIPSO to quantitatively evaluate aerosol simulations from climate models. Our analyses show that the global means in AOD climatology from NCAR CAM5 and GFDL AM3 simulations are comparable with satellite measurements. However, the overall correlation coefficient between the AOD spatial patterns from CAM5 and satellite is only 0.4. Moreover, at finer scales, the magnitude of AOD in CAM5 is much lower than satellite measurements for most of the non-dust regions, especially over East Asia. GFDL AM3 shows better AOD simulations over East Asia. The underestimated AOD over remote maritime areas in CAM5 was attributed to the unrealistic wet removal processes in convective clouds of CAM5. Over continents, biases on AOD could stem from underestimations in the emissions inventory and unresolved sub-grid variations of relative humidity due to the model's coarse resolution. Uncertainty from emission inventory over developing countries in East Asia will be assessed using the newly updated Regional Emission inventory in Asia (REAS) and Multi-resolution Emission Inventory in China (MEIC) in the model simulations.

  1. Classification of Aerosol over Central Europe by Cluster Analysis of Aerosol Columnar Optical Properties and Backward Trajectory Statistics

    NASA Astrophysics Data System (ADS)

    Szkop, Artur; Pietruczuk, Aleksander; Posyniak, Michał

    2016-12-01

    A cluster analysis is applied to the Aerosol Robotic Network (AERONET) data obtained at Belsk, Poland, as well as three nearby Central European stations (Leipzig, Minsk and Moldova) for estimation of atmospheric aerosol types. Absorption Ångstrom exponent (AAE), aerosol optical thickness (AOT) and extinction Ångstrom exponent (EAE) parameters are used. Clustering in both 2D (AOT, EAE) and 3D (AOT, EAE, AAE) is investigated. A method of air mass backward trajectory analysis is then proposed, with the receptor site at Belsk, to determine possible source regions for each cluster. Four dominant aerosol source regions are identified. The biomass burning aerosol source is localized in the vicinity of Belarusian-Ukrainian border. Slovakia and northern Hungary are found to be the source of urban/industrial pollutants. Western Poland and eastern Germany are the main sources of polluted continental aerosols. The most differentiated source region of Scandinavia, Baltic Sea and Northern Atlantic, associated with lowest values of AOT, corresponds to clean continental and possibly maritime type aerosols.

  2. Optical properties and aging of light-absorbing secondary organic aerosol

    DOE PAGES

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; ...

    2016-10-14

    The light-absorbing organic aerosol (OA) commonly referred to as “brown carbon” (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NOx concentrations, photolysis time, and relative humidity (RH) on the light absorptionmore » of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.« less

  3. Vertical Profile of Aerosol Properties at Pico Mountain, Azores

    NASA Astrophysics Data System (ADS)

    Wright, K.; Mazzoleni, C.; Mazzoleni, L. R.; Dzepina, K.; Hueber, J.; China, S.; Sharma, N.

    2013-12-01

    of aerosol properties in a marine environment from the boundary layer to the free troposphere. The analysis of these data will help us understand the role of aerosol aging, vertical transport and distribution in a marine environment.

  4. Ground-based remote sensing of aerosol optical properties and their radiative impacts in PRD region of China

    NASA Astrophysics Data System (ADS)

    Mai, Boru; Deng, XueJiao; Li, Zhanqing; Li, Fei; Zou, Yu; Deng, Tao; Liu, Xiantong

    2015-04-01

    Aerosol direct effects on surface irradiance were explored by using 7 years' ground-based broadband and spectral radiation data at Panyu, the main site of atmospheric composition monitoring in Pearl River Delta (PRD) . Aerosol optical properties were derived from a Sun photometer, and the radiations were calculated by SBDART model. Results demonstrated that in dry seasons(from October to next February), the annual mean aerosol optical depth (AOD) at 550nm was 0.535, and more than 60% AOD was in a range of 0.2-0.6. Due to the fact that few dust taken place in PRD region, the course mode of weak or strong absorbing aerosol was negligible. However, the proportion of fine mode, weak radiation absorbing particle was about 9.52%, with the Angstrom exponent (α440/470) = 1.30, single scatter co-albedo (ω0) =0.04.Up to 90% of the aerosol was dominated by fine mode, strong absorbing particles, as given by mean α440/470 = 1.35, ω0 =0.14. Because of strong absorption, the variations in aerosol concentration significantly heated the air, and cooled down the surface. The annual mean shortwave direct radiation forcing at the surface (SFC), inside the atmosphere (ATM), and at the top of atmosphere (TOA) was -33.51

  5. Radiative properties of Bay of Bengal aerosols: Spatial distinctiveness and source impacts

    NASA Astrophysics Data System (ADS)

    Babu, S. Suresh; Gogoi, Mukunda M.; Kumar, V. H. Arun; Nair, Vijayakumar S.; Moorthy, K. Krishna

    2012-03-01

    Simultaneous and collocated measurements of spectrally resolved scattering and absorption coefficients and mass concentration of near-surface composite aerosols in the marine atmosphere over the Bay of Bengal (BOB), along with incoming shortwave (0.3-3 μm) global solar radiation and columnar spectral aerosol optical depths (AOD), were made on a research cruise during the winter phase of the Integrated Campaign for Aerosols, Gases and Radiation Budget (W-ICARB). The aerosol radiative properties revealed distinct spatial features associated with the contrasting outflows from Indo-Gangetic Plain (IGP) and East Asia. Both scattering and absorption coefficients depicted very high values (>200 and >15 Mm-1) over the northwestern and southeastern BOB and extremely low values (<50 and <10 Mm-1) over the central BOB. The mean value of the total scattering coefficient at 550 nm (˜123.7 ± 85.3 Mm-1) over the entire BOB during winter was higher than the mean values (˜94 ± 47 Mm-1) reported for the premonsoon season. While SSA at 550 nm showed very low values (<0.8) over a very large region in the central BOB and moderately low values over the southern BOB (˜0.85-0.9), the columnar AOD varied from the least values of ˜0.1 over the northeastern BOB to the highest values of ˜0.8 over the northwestern BOB. While significant cooling was observed at the top of the atmosphere and surface over the northwestern BOB, the atmospheric forcing was found to be significantly high (˜15 W m-2) over the southern BOB, where the aerosol radiative forcing efficiency (ARFE) at the surface was also found to be high. Examination of the Moderate Resolution Imaging Spectroradiometer (MODIS)-derived fire count along with the advection pathways revealed a strong contribution from the emissions of biomass smoke from East Asia, which might be contributing to the enhanced aerosol induced warming over the southern BOB. However, the ARFE at the surface was low over the northwestern BOB, where the

  6. Optical properties of mineral dust aerosol in the thermal infrared

    NASA Astrophysics Data System (ADS)

    Köhler, Claas H.

    2017-02-01

    The optical properties of mineral dust and biomass burning aerosol in the thermal infrared (TIR) are examined by means of Fourier Transform Infrared Spectrometer (FTIR) measurements and radiative transfer (RT) simulations. The measurements were conducted within the scope of the Saharan Mineral Dust Experiment 2 (SAMUM-2) at Praia (Cape Verde) in January and February 2008. The aerosol radiative effect in the TIR atmospheric window region 800-1200 cm-1 (8-12 µm) is discussed in two case studies. The first case study employs a combination of IASI measurements and RT simulations to investigate a lofted optically thin biomass burning layer with emphasis on its potential influence on sea surface temperature (SST) retrieval. The second case study uses ground based measurements to establish the importance of particle shape and refractive index for benchmark RT simulations of dust optical properties in the TIR domain. Our research confirms earlier studies suggesting that spheroidal model particles lead to a significantly improved agreement between RT simulations and measurements compared to spheres. However, room for improvement remains, as the uncertainty originating from the refractive index data for many aerosol constituents prohibits more conclusive results.

  7. Laboratory studies on optical properties of secondary organic aerosols generated during the photooxidation of toluene and the ozonolysis of α-pinene

    NASA Astrophysics Data System (ADS)

    Nakayama, Tomoki; Matsumi, Yutaka; Sato, Kei; Imamura, Takashi; Yamazaki, Akihiro; Uchiyama, Akihiro

    2010-12-01

    It has recently been suggested that some organic aerosols can absorb solar radiation, especially at the shorter visible and UV wavelengths. Although quantitative characterization of the optical properties of secondary organic aerosols (SOAs) is required in order to confirm the effect of SOAs on the atmospheric radiation balance, the light absorption of SOAs has not yet been thoroughly investigated. In this study, we conducted laboratory experiments to measure the optical properties of SOAs generated during the photooxidation of toluene in the presence of NOx and the ozonolysis of α-pinene. Extinction and scattering coefficients of the SOAs were measured by a cavity ring-down aerosol extinction spectrometer and an integrating nephelometer, respectively. Refractive indices of the SOAs were determined so that the measured particle size dependence of the extinction and scattering efficiencies could be reproduced by calculations using Mie scattering theory. As a result, significant light absorption was found at 355 nm for the toluene SOAs. In contrast, no significant absorption was found either at 355 or 532 nm for the α-pinene SOAs. Using the obtained refractive index, mass absorption cross-section values of the toluene SOAs were calculated to be 0.3-3 m2 g-1 at 355 nm. The results indicate that light absorption by the SOAs formed from the photooxidation of aromatic hydrocarbons have a potential to influence the total aerosol light absorption, especially at UV wavelengths.

  8. Far-IR Absorption Features of Titan Aerosol Analogs Produced from Aromatic Precursors

    NASA Astrophysics Data System (ADS)

    Sebree, Joshua; Trainer, M. G.; Anderson, C. M.; Loeffler, M. J.

    2012-10-01

    The arrival of the Cassini spacecraft in orbit around Saturn has led to the discovery of benzene (C6H6) at ppm levels, as well as large positive ions in Titan’s atmosphere, tentatively identified as polycyclic aromatic hydrocarbons (PAHs).[1] The presence of aromatic molecules, which are photolytically active in the ultraviolet, may be an important part of the formation of aerosol particles in Titan’s haze layers, even at these low concentrations. To date, there have been no laboratory experiments in the literature exploring this area of study. The analysis of data from the Composite Infrared Spectrometer (CIRS) on-board Cassini has recently uncovered a broad emission feature centered at 140 cm-1 in the far-IR that is unique to the aerosol layers of Titan’s atmosphere.[2] Current optical constants from laboratory-generated aerosol analogs have been unable to reproduce this feature.[3,4] From the broadness of this feature, we speculate that the emission is a blended composite of low-energy vibrations of large molecules such as PAHs and their nitrogen containing counterparts, polycyclic aromatic nitrogen heterocycles (PANHs). We hypothesize that the inclusion of trace amounts of aromatic precursors will aid in the production of these large structures in the laboratory-generated aerosols. In this study, we perform UV irradiation of several aromatic precursors, both with and without nitrogen heteroatoms, to understand their influence on the observable characteristics of the aerosol. Measured optical and chemical properties will be compared to those formed from CH4/N2 mixtures [5,6] as well as to those from Cassini observations. [1] Waite, J. H., et al. (2007) Science 316 870-875. [2] Anderson, C.M, et al. (2011) Icarus 212 762-778. [3] Khare, B.N., et al. (1984) Icarus 60 127-137. [4] Imanaka, H., et al. (2012) Icarus 218 247-261. [5] Trainer, M.G., et al. (2006) PNAS 103 18035-18042. [6] Trainer, M.G., et al. (2012) Astrobiology 12 315-326.

  9. Hygroscopic, Morphological, and Chemical Properties of Agricultural Aerosols

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Brooks, S. D.; Cheek, L.; Thornton, D. C.; Auvermann, B. W.; Littleton, R.

    2007-12-01

    Agricultural fugitive dust is a significant source of localized air pollution in the semi-arid southern Great Plains. In the Texas Panhandle, daily episodes of ground-level fugitive dust emissions from the cattle feedlots are routinely observed in conjunction with increased cattle activity in the late afternoons and early evenings. We conducted a field study to characterize size-selected agricultural aerosols with respect to hygroscopic, morphological, and chemical properties and to attempt to identify any correlations between these properties. To explore the hygroscopic nature of agricultural particles, we have collected size-resolved aerosol samples using a cascade impactor system at a cattle feedlot in the Texas Panhandle and have used the Environmental Scanning Electron Microscope (ESEM) to determine the water uptake by individual particles in those samples as a function of relative humidity. To characterize the size distribution of agricultural aerosols as a function of time, A GRIMM aerosol spectrometer and Sequential Mobility Particle Sizer and Counter (SMPS) measurements were simultaneously performed in an overall size range of 11 nm to 20 µm diameters at a cattle feedlot. Complementary determination of the elemental composition of individual particles was performed using Energy Dispersive X-ray Spectroscopy (EDS). In addition to the EDS analysis, an ammonia scrubber was used to collect ammonia and ammonium in the gas and particulate phases, respectively. The concentration of these species was quantified offline via UV spectrophotometry at 640 nanometers. The results of this study will provide important particulate emission data from a feedyard, needed to improve our understanding of the role of agricultural particulates in local and regional air quality.

  10. Ice Nucleation Properties of Amospherically Aged Biomass Burning Aerosol

    NASA Astrophysics Data System (ADS)

    Polen, M.; Lawlis, E.; Sullivan, R. C.

    2015-12-01

    Biomass burning can sometimes emit surprisingly active ice nucleating particles, though these emissions are not at all consistent between biomass fuel sources and burns. Soot from biomass combustion has been attributed to some but not all of the ice nucleating potential of biomass burning aerosol (BBA), while fossil fuel combustion soot emits very weak ice nucleants. The causes of the sometimes significant but variable ice nucleating ability of BBA are still largely unknown. BBA experiences significant atmospheric aging as the plume evolves and mixes with background air, yet almost no reports exploring the effects of atmospheric aging on the freezing properties of BBA have been made. We have performed some of the first experiments to determine the effects of simulated atmospheric aging on these ice nucleation properties, using a chamber reactor. The fresh and aged BBA was collected for subsequent droplet freezing array analysis using an impinger sampler to collect aerosol in water, and by deposition onto substrates in a MOUDI sampler. Droplets containing the chamber particles were then suspended in oil on a cold plate for freezing temperature spectrum measurement. Aging of Sawgrass flaming-phase combustion BBA by exposure to hydroxyl radicals (from H2O2 photolysis) enhanced the ice nucleation ability, observed by a shift to warmer droplet freezing temperatures by ~2-3°C. The changes in the aerosol's chemical composition during aging were observed using a laser ablation single-particle mass spectrometer and a soot-particle aerosol mass spectrometer. We will report our observations of the effects of other types of simulated aging (including photochemistry under high and low NOx conditions, dark ozonolysis, and nitric acid exposure) on Sawgrass and BBA from other grass and palm fuels.

  11. Physical and Chemical Properties of Anthropogenic Aerosols: An Overview

    EPA Science Inventory

    Aerosol chemical composition is complex. Combustion aerosols can comprise tens of thousands of organic compounds, refractory brown and black carbon, heavy metals, cations, anions, salts, and other inorganic phases. Aerosol organic matter normally contains semivolatile material th...

  12. The Effects of Mineral Dust on the Hygroscopic and Optical Properties of Inorganic Salt Aerosols

    NASA Astrophysics Data System (ADS)

    Attwood, A. R.; Greenslade, M. E.

    2011-12-01

    Mineral dust particles are a significant fraction of the total aerosol mass, thus they play an important role in the Earth's radiative budget by direct scattering and absorption of radiation. Assessing this impact is complicated by the variability of optical properties resulting from water uptake and changes in chemical composition due to atmospheric mixing. Internal mixtures of montmorillonite, a clay component of mineral dust, with sodium chloride and ammonium sulfate were studied optically using cavity ring down spectroscopy. The effects of the addition of the clay to the optically observed deliquescence relative humidity (DRH) and water uptake of these salts was considered by investigating a series of different salt mass fractions. In most cases, montmorillonite alters the hygroscopic properties and causes the DRH to occur at a lower relative humidity. For ammonium sulfate, optical properties can be approximated by volume weighted mixing rules with some minor deviations around the DRH. For sodium chloride, this approximation is only accurate below the DRH with enhanced water uptake at higher relative humidities. Our results show that salt particles may transition from solid to liquid at a lower relative humidity than is expected based on the salt alone, as observed with changes in optical properties. Further, they contradict current measurements in the literature that suggest little change in the hygroscopic behavior of salts when insoluble mineral dust components are added and should continue to be investigated. Accurate, direct measurements of the effect of the addition of clays to the optical properties of common aerosol species will allow for improvements in the prediction of the aerosol direct effect.

  13. Global volcanic aerosol properties derived from emissions, 1990-2014, using CESM1(WACCM): VOLCANIC AEROSOLS DERIVED FROM EMISSIONS

    SciTech Connect

    Mills, Michael J.; Schmidt, Anja; Easter, Richard; Solomon, Susan; Kinnison, Douglas E.; Ghan, Steven J.; Neely, Ryan R.; Marsh, Daniel R.; Conley, Andrew; Bardeen, Charles G.; Gettelman, Andrew

    2016-03-06

    Accurate representation of global stratospheric aerosol properties from volcanic and non-volcanic sulfur emissions is key to understanding the cooling effects and ozone-loss enhancements of recent volcanic activity. Attribution of climate and ozone variability to volcanic activity is of particular interest in relation to the post-2000 slowing in the apparent rate of global average temperature increases, and variable recovery of the Antarctic ozone hole. We have developed a climatology of global aerosol properties from 1990 to 2014 calculated based on volcanic and non-volcanic emissions of sulfur sources. We have complied a database of volcanic SO2 emissions and plume altitudes for eruptions between 1990 and 2014, and a new prognostic capability for simulating stratospheric sulfate aerosols in version 5 of the Whole Atmosphere Community Climate Model, a component of the Community Earth System Model. Our climatology shows remarkable agreement with ground-based lidar observations of stratospheric aerosol optical depth (SAOD), and with in situ measurements of aerosol surface area density (SAD). These properties are key parameters in calculating the radiative and chemical effects of stratospheric aerosols. Our SAOD climatology represents a significant improvement over satellite-based analyses, which ignore aerosol extinction below 15 km, a region that can contain the vast majority of stratospheric aerosol extinction at mid- and high-latitudes. Our SAD climatology significantly improves on that provided for the Chemistry-Climate Model Initiative, which misses 60% of the SAD measured in situ. Our climatology of aerosol properties is publicly available on the Earth System Grid.

  14. Polycyclic aromatic hydrocarbons in biomass-burning emissions and their contribution to light absorption and aerosol toxicity.

    PubMed

    Samburova, Vera; Connolly, Jessica; Gyawali, Madhu; Yatavelli, Reddy L N; Watts, Adam C; Chakrabarty, Rajan K; Zielinska, Barbara; Moosmüller, Hans; Khlystov, Andrey

    2016-10-15

    In recent years, brown carbon (BrC) has been shown to be an important contributor to light absorption by biomass-burning atmospheric aerosols in the blue and near-ultraviolet (UV) part of the solar spectrum. Emission factors and optical properties of 113 polycyclic aromatic hydrocarbons (PAHs) were determined for combustion of five globally important fuels: Alaskan, Siberian, and Florida swamp peat, cheatgrass (Bromus tectorum), and ponderosa pine (Pinus ponderosa) needles. The emission factors of total analyzed PAHs were between 1.9±0.43.0±0.6 and 9.6±1.2-42.2±5.4mgPAHkg(-1)fuel for particle- and gas phase, respectively. Spectrophotometric analysis of the identified PAHs showed that perinaphthenone, methylpyrenes, and pyrene contributed the most to the total PAH light absorption with 17.2%, 3.3 to 10.5%, and 7.6% of the total particle-phase PAH absorptivity averaged over analyzed emissions from the fuels. In the gas phase, the top three PAH contributors to BrC were acenaphthylene (32.6%), anthracene (8.2%), and 2,4,5-trimethylnaphthalene (8.0%). Overall, the identified PAHs were responsible for 0.087-0.16% (0.13% on average) and 0.033-0.15% (0.11% on average) of the total light absorption by dichloromethane-acetone extracts of particle and gas emissions, respectively. Toxic equivalency factor (TEF) analysis of 16 PAHs prioritized by the United States Environmental Protection Agency (EPA) showed that benzo(a)pyrene contributed the most to the PAH carcinogenic potency of particle phase emissions (61.8-67.4% to the total carcinogenic potency of Σ16EPA PAHs), while naphthalene played the major role in carcinogenicity of the gas phase PAHs in the biomass-burning emission analyzed here (35.4-46.0% to the total carcinogenic potency of Σ16EPA PAHs). The 16 EPA-prioritized PAHs contributed only 22.1±6.2% to total particle and 23.4±11% to total gas phase PAH mass, thus toxic properties of biomass-burning PAH emissions are most likely underestimated.

  15. 2014 iAREA campaign on aerosol in Spitsbergen - Part 1: Study of physical and chemical properties

    NASA Astrophysics Data System (ADS)

    Lisok, J.; Markowicz, K. M.; Ritter, C.; Makuch, P.; Petelski, T.; Chilinski, M.; Kaminski, J. W.; Becagli, S.; Traversi, R.; Udisti, R.; Rozwadowska, A.; Jefimow, M.; Markuszewski, P.; Neuber, R.; Pakszys, P.; Stachlewska, I. S.; Struzewska, J.; Zielinski, T.

    2016-09-01

    This paper presents the results of measurements of aerosol physical and chemical properties during iAREA2014 campaign that took place on Svalbard between 15th of Mar and 4th of May 2014. With respect to field area, the experiment consisted of two sites: Ny-Ålesund (78°55‧N, 11°56‧E) and Longyearbyen (78°13‧N, 15°33‧E) with further integration of Aerosol Robotic Network (AERONET) station in Hornsund (77°00‧N, 15°33‧E). The subject of this study is to investigate the in-situ, passive and active remote sensing observations as well as numerical simulations to describe the temporal variability of aerosol single-scattering properties during spring season on Spitsbergen. The retrieval of the data indicates several event days with enhanced single-scattering properties due to the existence of sulphate and additional sea-salt load in the atmosphere which is possibly caused by relatively high wind speed. Optical results were confirmed by numerical simulations made by the GEM-AQ model and by chemical observations that indicated up to 45% contribution of the sea-salt to a PM10 total aerosol mass concentration. An agreement between the in-situ optical and microphysical properties was found, namely: the positive correlation between aerosol scattering coefficient measured by the nephelometer and effective radius obtained from laser aerosol spectrometer as well as negative correlation between aerosol scattering coefficient and the Ångstrom exponent indicated that slightly larger particles dominated during special events. The in-situ surface observations do not show any significant enhancement of the absorption coefficient as well as the black carbon concentration which might occur during spring. All of extensive single-scattering properties indicate a diurnal cycle in Longyearbyen, where 21:00-5:00 data stays at the background level, however increasing during the day by the factor of 3-4. It is considered to be highly connected with local emissions originating

  16. Constraining Black Carbon Aerosol over Asia using OMI Aerosol Absorption Optical Depth and the Adjoint of GEOS-Chem

    NASA Technical Reports Server (NTRS)

    Zhang, Li; Henze, David K.; Grell, Georg A.; Carmichael. Gregory R.; Bousserez, Nicolas; Zhang, Qiang; Torres, Omar; Ahn, Changwoo; Lu, Zifeng; Cao, Junji; Mao, Yuhao

    2015-01-01

    Accurate estimates of the emissions and distribution of black carbon (BC) in the region referred to here as Southeastern Asia (70degE-l50degE, 11degS-55degN) are critical to studies of the atmospheric environment and climate change. Analysis of modeled BC concentrations compared to in situ observations indicates levels are underestimated over most of Southeast Asia when using any of four different emission inventories. We thus attempt to reduce uncertainties in BC emissions and improve BC model simulations by developing top-down, spatially resolved, estimates of BC emissions through assimilation of OMI observations of aerosol absorption optical depth (AAOD) with the GEOS-Chem model and its adjoint for April and October of 2006. Overwhelming enhancements, up to 500%, in anthropogenic BC emissions are shown after optimization over broad areas of Southeast Asia in April. In October, the optimization of anthropogenic emissions yields a slight reduction (1-5%) over India and parts of southern China, while emissions increase by 10-50% over eastern China. Observational data from in situ measurements and AERONET observations are used to evaluate the BC inversions and assess the bias between OMI and AERONET AAOD. Low biases in BC concentrations are improved or corrected in most eastern and central sites over China after optimization, while the constrained model still underestimates concentrations in Indian sites in both April and October, possibly as a. consequence of low prior emissions. Model resolution errors may contribute up to a factor of 2.5 to the underestimate of surface BC concentrations over northern India. We also compare the optimized results using different anthropogenic emission inventories and discuss the sensitivity of top-down constraints on anthropogenic emissions with respect to biomass burning emissions. In addition, the impacts of brown carbon, the formulation of the observation operator, and different a priori constraints on the optimization are

  17. Sensitivity of aerosol optical depth, single scattering albedo, and phase function calculations to assumptions on physical and chemical properties of aerosol

    EPA Science Inventory

    In coupled chemistry-meteorology simulations, the calculation of aerosol optical properties is an important task for the inclusion of the aerosol effects on the atmospheric radiative budget. However, the calculation of these properties from an aerosol profile is not uniquely defi...

  18. Diurnal Evolution of Aerosol Optical Properties and Morphology at Pico Tres Padres: A Phenomenological Analysis

    NASA Astrophysics Data System (ADS)

    Mazzoleni, C.; Chakrabarty, R.; Dubey, M. K.; Moosmuller, H.; Chylek, P.; Onasch, T. B.; Herndon, S.; Zavala, M.; Kolb, C.

    2007-05-01

    Aerosol optical properties affect planetary radiative balance and therefore climate. The optical properties are related to chemical composition, size distribution, and morphology, which also have implications for human health and environmental degradation. During the MILAGRO field campaign, we measured ensemble aerosol absorption and angle-integrated scattering in Mexico City. These measurements were performed using the Los Alamos aerosol photoacoustic instrument with an integrated nephelometer (LAPA) operating at 781 nm. The LAPA was mounted on-board the Aerodyne Inc. mobile laboratory, which hosted a wide variety of gaseous and aerosol instruments. During the campaign, the Aerodyne mobile laboratory was moved to different sites, capturing the influence of spatial and temporal parameters including location, aging, elevation, and sources on ambient air pollution. The LAPA operated almost continuously between the 3rd and the 28th of March 2006. During the same period we collected ambient aerosols on more than 100 Nuclepore filters for scanning electron microscopy (SEM) analysis. Filter samples were collected during specific pollution events and different times of the day. Subsequently, SEM images of selected filters were taken to study particle morphology. The elemental composition of a few individual particles was also qualitatively assessed by energy dispersive X-ray spectroscopy. Between March 7th and 19th the laboratory was sampling air close to the top of the Pico Tres Padres, a ~3000 m high mountain on the north side of the Mexico City. Daily changes of aerosol loading and pollutant concentrations followed the expected diurnal variations of the boundary layer height. Here we report a preliminary analysis of aerosol absorption, scattering, and morphology at Pico Tres Padres for three specific days (9th, 11th and 12th of March 2006). The single scattering albedo (ratio of scattering to total extinction) during these three days showed a characteristic drop in the

  19. Aerosols optical properties in Titan's Detached Haze Layer

    NASA Astrophysics Data System (ADS)

    Seignovert, Benoit; Rannou, Pascal; Lavvas, Panayotis; West, Robert

    2016-10-01

    Titan's Detached Haze Layer (DHL) was first observed in 1983 by Rages and Pollack during the Voyager 2 is a consistent spherical haze feature surrounding Titan's upper atmosphere and detached from the main haze. Since 2005, the Imaging Science Subsystem (ISS) instrument on board the Cassini mission performs a continuous survey of the Titan's atmosphere and confirmed its persistence at 500 km up to the equinox (2009) before its drop and disappearance in 2012 (West et al. 2011). Previous analyses showed, that this layer corresponds to the transition area between small spherical aerosols and large fractal aggregates and play a key role in the aerosols formation in Titan's atmosphere (Rannou et al. 2000, Lavvas et al. 2009, Cours et al. 2011).In this talk we will present the UV photometric analyses based on radiative transfer inversion to retrieve aerosols particles properties in the DHL (bulk and monomer radius and local density) performed on ISS observations taken from 2005 to 2007.References:- Rages and Pollach, Icarus 55 (1983)- West, et al., Icarus 38 (2011)- Rannou, et al., Icarus 147 (2000)- Lavvas, et al., Icarus 201 (2009)- Cours, et al., ApJ Lett. 741 (2015)

  20. Aerosol optical properties from multiwavelength lidar measurements in Romania

    NASA Astrophysics Data System (ADS)

    Nicolae, Doina; Talianu, Camelia; Carstea, Emil; Nemuc, Anca

    2009-09-01

    Vertically resolved profiles of optical properties of aerosols were measured using a multi-wavelength lidar system-RALI, set up at the scientific research center in Magurele, Bucharest area (44.35 N latitude, 26.03 E longitude) during 2008. The use of multiple laser wavelengths has enabled us to observe significant variations in backscatter profiles depending on the particle origins. An air mass backward trajectory analysis, using Hysplit-4, was carried out to track the aerosol plumes. Aerosols can serve as valuable tracers of air motion in the planetary boundary layer (PBL). The height of layers in the lower troposphere from lidar signal was calculated using the gradient method- minima of the first derivative. The Richardson number method was used to estimate PBL height from the radio-soundings. We have used pressure, temperature and dew point profiles as well as the wind direction profiles from NOAA (National Oceanic and Atmospheric Administration) data base. The results were consistent with the ones obtained from LIDAR.

  1. Optical Properties and Mixing State of Aerosols from Residential Wood Burning and Vehicle Emissions in Central and Southern California

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Cappa, C. D.; Collier, S.; Zhang, Q.; Williams, L. R.; Lee, A.; Abbatt, J.; Russell, L. M.; Liu, J.; Chen, C. L.; Betha, R.

    2015-12-01

    Light-absorbing materials such as black carbon (BC) and brown carbon (BrC) in atmospheric aerosols play important roles in regulating the earth's radiative budget and climate. However, the representations of BC and BrC in state-of-the-art climate models remain highly uncertain, in part due to the poor understanding of their microphysical and optical properties. Direct observations and characterizations of the mixing state and absorption enhancement of ambient aerosols could provide invaluable constraints for current model representations of aerosol radiative effects. Here, we will discuss results from measurements of aerosol light absorption and absorption enhancement (Eabs), using a thermodenuder-absorption method, made during two recent field studies in central and southern California. The winter study took place in Dec/Jan of 2014/2015 in Fresno, CA. This region is severely impacted by particulate matter from local and regional residential biomass burning. The summer study took place in July 2015 in Fontana, CA, a region ~80 km downwind of Los Angeles and strongly impacted by vehicular emissions, and thus provides a sharp contrast to the Fresno study. Eabs of BC particles due to the "lensing" effect from coatings to BC core and/or the presence of BrC will be quantified and compared between the two studies. Additionally, the chemical composition of bulk and the BC-containing particles are determined via a HR-ToF-AMS and a SP-AMS, respectively. Variations in the composition and mixing state of the ambient particles and how these affect the observed Eabs will be examined. The overall measurements suggest a relatively small role for lensing-induced absorption enhancements for ambient particles in these regions.

  2. Upper-atmosphere Aerosols: Properties and Natural Cycles

    NASA Technical Reports Server (NTRS)

    Turco, Richard P.

    1992-01-01

    The middle atmosphere is rich in its variety of particulate matter, which ranges from meteorite debris, to sulfate aerosols, to polar stratospheric ice clouds. Volcanic eruptions strongly perturb the stratospheric sulfate (Junge) layer. High-altitude 'noctilucent' ice clouds condense at the summer mesopause. The properties of these particles, including their composition, sizes, and geographical distribution, are discussed, and their global effects, including chemical, radiative, and climatic roles, are reviewed. Polar stratospheric clouds (PSCs) are composed of water and nitric acid in the form of micron-sized ice crystals. These particles catalyze reactions of chlorine compounds that 'activate' otherwise inert chlorine reservoirs, leading to severe ozone depletions in the southern polar stratosphere during austral spring. PSCs also modify the composition of the polar stratosphere through complex physiocochemical processes, including dehydration and denitrification, and the conversion of reactive nitrogen oxides into nitric acid. If water vapor and nitric acid concentrations are enhanced by high-altitude aircraft activity, the frequency, geographical range, and duration of PSCs might increase accordingly, thus enhancing the destruction of the ozone layer (which would be naturally limited in geographical extent by the same factors that confine the ozone hole to high latitudes in winter). The stratospheric sulfate aerosol layer reflects solar radiation and increases the planetary albedo, thereby cooling the surface and possibly altering the climate. Major volcanic eruptions, which increase the sulfate aerosol burden by a factor of 100 or more, may cause significant global climate anomalies. Sulfate aerosols might also be capable of activating stratospheric chlorine reservoirs on a global scale (unlike PCSs, which represent a localized polar winter phenomenon), although existing evidence suggests relatively minor perturbations in chlorine chemistry. Nevertheless, if

  3. Meteorological and aerosol effects on marine cloud microphysical properties

    NASA Astrophysics Data System (ADS)

    Sanchez, K. J.; Russell, L. M.; Modini, R. L.; Frossard, A. A.; Ahlm, L.; Corrigan, C. E.; Roberts, G. C.; Hawkins, L. N.; Schroder, J. C.; Bertram, A. K.; Zhao, R.; Lee, A. K. Y.; Lin, J. J.; Nenes, A.; Wang, Z.; Wonaschütz, A.; Sorooshian, A.; Noone, K. J.; Jonsson, H.; Toom, D.; Macdonald, A. M.; Leaitch, W. R.; Seinfeld, J. H.

    2016-04-01

    Meteorology and microphysics affect cloud formation, cloud droplet distributions, and shortwave reflectance. The Eastern Pacific Emitted Aerosol Cloud Experiment and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets studies provided measurements in six case studies of cloud thermodynamic properties, initial particle number distribution and composition, and cloud drop distribution. In this study, we use simulations from a chemical and microphysical aerosol-cloud parcel (ACP) model with explicit kinetic drop activation to reproduce observed cloud droplet distributions of the case studies. Four cases had subadiabatic lapse rates, resulting in fewer activated droplets, lower liquid water content, and higher cloud base height than an adiabatic lapse rate. A weighted ensemble of simulations that reflect measured variation in updraft velocity and cloud base height was used to reproduce observed droplet distributions. Simulations show that organic hygroscopicity in internally mixed cases causes small effects on cloud reflectivity (CR) (<0.01), except for cargo ship and smoke plumes, which increased CR by 0.02 and 0.07, respectively, owing to their high organic mass fraction. Organic hygroscopicity had larger effects on droplet concentrations for cases with higher aerosol concentrations near the critical diameter (namely, polluted cases with a modal peak near 0.1 µm). Differences in simulated droplet spectral widths (k) caused larger differences in CR than organic hygroscopicity in cases with organic mass fractions of 60% or less for the cases shown. Finally, simulations from a numerical parameterization of cloud droplet activation suitable for general circulation models compared well with the ACP model, except under high organic mass fraction.

  4. Wintertime aerosol properties during foggy and nonfoggy days over urban center Delhi and their implications for shortwave radiative forcing

    NASA Astrophysics Data System (ADS)

    Ganguly, Dilip; Jayaraman, A.; Rajesh, T. A.; Gadhavi, H.

    2006-08-01

    We present results from complimentary measurements of physical and optical properties of aerosols carried out at Delhi, as part of the Indian Space Research Organization Geosphere Biosphere Programme's Land Campaign II in December 2004. For the first time we unravel ground truth values of several radiatively important aerosol parameters such as their wavelength dependency in absorption, scattering behavior, single-scattering albedo, number size distribution, and vertical distribution in the atmosphere from this polluted megacity in south Asia. Interesting features are observed in the behavior of aerosol parameters under intermittent foggy, hazy, and clear-sky conditions prevalent during the campaign. All aerosol parameters exhibited a large distribution in their values, with variabilities being particularly higher on hazy and foggy days. The average clear-sky aerosol optical depth (AOD) value is 0.91 ± 0.48, which is higher than the AOD value reported for most other cities in India during this season of the year. Increases in AOD on hazy and foggy days are found to be spectrally nonuniform. The percentage increase in AOD at shorter wavelengths was higher on hazy days compared to clear days. Diurnally averaged BC mass concentration varied from a low of 15 μg/m3 during clear days to a high of about 65 μg/m3 on hazy days. The wavelength dependency of aerosol absorption shows signatures of the presence of a significant amount of absorbing aerosols produced from biofuel/biomass burning. Single-scattering albedo at 525 nm is found to vary between 0.6 and 0.8 with an average value of 0.68 for the entire period. Lidar observations reveal that during a fog event there is a subsidence of aerosols to an extremely dense and shallow atmospheric layer of less than 200 m height from the surface. The presence of an aerosol layer at elevated altitudes is also detected. All the results are combined and used for estimating aerosol radiative forcing using a discrete ordinate

  5. Hygroscopic properties of different aerosol types over the Atlantic and Indian Oceans

    NASA Astrophysics Data System (ADS)

    Maßling, A.; Wiedensohler, A.; Busch, B.; Neusüß, C.; Quinn, P.; Bates, T.; Covert, D.

    2003-01-01

    Hygroscopic properties of atmospheric particles were studied in the marine tropospheric boundary layer over the Atlantic and Indian Oceans during two consecutive field studies: the Aerosols99 cruise (Atlantic Ocean) from 15 January to 20 February 1999, and the INDOEX cruise (Indian Ocean Experiment) from 23 February to 30 March 1999. The hygroscopic properties were compared to optical and chemical properties, such as absorption, chemical inorganic composition, and mass concentration of organic and elemental carbon, to identify the influence of these parameters on hygroscopicity. During the two field studies, four types of aerosol-sampling instruments were used on board the NOAA (Northern Organization Atlantic Administration) Research Vessel Ronald H Brown: Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA), seven-stage cascade impactor, two-stage cascade impactor, and Particle Soot Absorption Photometer (PSAP). The HTDMA was used to determine the hygroscopic properties of atmospheric particles at initial dry sizes (Dp) of 50, 150, and 250 nm and at relative humidities (RH) of 30, 55, 75, and 90%. The HTDMA data provide insight into the mixing state of the aerosol in terms of its hygroscopic behavior. Simultaneously, a seven-stage cascade impactor (3 in the sub-µm size range) was used to determine the molar composition of the major inorganic ions such as ammonium and sulfate ions. A two-stage cascade impactor (1 in the sub-µm size range, 1 in the sup-µm size range) was used to determine the mass concentration of organic and elemental carbon. The PSAP was used (at a wavelength of 565 nm) to measure the light absorption coefficient of the aerosol. During the two field studies, air masses of several different origins passed the ship's cruise path. The air mass back-trajectory analysis revealed marine air masses as well as air masses with continental influence from Africa, India, or Arabia. The occurrence of different air masses was classified into special

  6. In-Situ Measurements of Aerosol Optical and Hygroscopic Properties at the Look Rock Site during SOAS 2013

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Zimmermann, K.; Bertram, T. H.; Corrigan, A. L.; Guzman, J. M.; Russell, L. M.; Budisulistiorini, S.; Li, X.; Surratt, J. D.; Hicks, W.; Bairai, S. T.; Cappa, C. D.

    2013-12-01

    One of the main goals of the Southern Oxidant and Aerosol Study (SOAS) is to characterize the climate-relevant properties of aerosols over the southeastern United States at the interface of biogenic and anthropogenic emissions. As part of the SOAS campaign, the UCD cavity ringdown/photoacoustic spectrometer was deployed to make in-situ measurements of aerosol light extinction, absorption and sub-saturated hygroscopicity at the Look Rock site (LRK) in the Great Smoky Mountains National Park, TN from June 1 to July 15, 2013. The site is influenced by substantial biogenic emissions with varying impacts from anthropogenic pollutants, allowing for direct examination of the optical and hygroscopic properties of anthropogenic-influenced biogenic secondary organic aerosols (SOA). During the experiment period, the average dry aerosol extinction (Bext), absorption (Babs) coefficients and single scattering albedo (SSA) at 532 nm were 30.3 × 16.5 Mm-1, 1.12 × 0.78 Mm-1 and 0.96 × 0.06. The Babs at 532 nm was well correlated (r2 = 0.79) with the refractory black carbon (rBC) number concentration determined by a single particle soot spectrometer (SP2). The absorption by black carbon (BC), brown carbon (BrC) and the absorption enhancement due to the 'lensing' effect were quantified by comparing the Babs of ambient and thermo-denuded aerosols at 405 nm and 532 nm. The optical sub-saturated hygroscopic growth factor was derived from extinction and particle size distribution measurements at dry and elevated relative humidity. In addition, to explore the extent to which ammonia mediated chemistry leads to BrC formation, as suggested in recent laboratory studies(1,2), we performed an NH3 perturbation experiment in-situ for 1 week during the study, in which ambient aerosols were exposed to approximately 100 ppb NH3 with a residence time of ~ 3hr. The broader implications of these observational data at LRK will be discussed in the context of the concurrent gas and aerosol chemical

  7. Microphysical, chemical and optical aerosol properties in the Baltic Sea region

    NASA Astrophysics Data System (ADS)

    Kikas, Ülle; Reinart, Aivo; Pugatshova, Anna; Tamm, Eduard; Ulevicius, Vidmantas

    2008-11-01

    The microphysical structure, chemical composition and prehistory of aerosol are related to the aerosol optical properties and radiative effect in the UV spectral range. The aim of this work is the statistical mapping of typical aerosol scenarios and adjustment of regional aerosol parameters. The investigation is based on the in situ measurements in Preila (55.55° N, 21.00° E), Lithuania, and the AERONET data from the Gustav Dalen Tower (58 N, 17 E), Sweden. Clustering of multiple characteristics enabled to distinguish three aerosol types for clear-sky periods: 1) clean maritime-continental aerosol; 2) moderately polluted maritime-continental aerosol; 3) polluted continental aerosol. Differences between these types are due to significant differences in aerosol number and volume concentration, effective radius of volume distribution, content of SO 4- ions and Black Carbon, as well as different vertical profiles of atmospheric relative humidity. The UV extinction, aerosol optical depth (AOD) and the Ångstrom coefficient α increased with the increasing pollution. The value α = 1.96 was observed in the polluted continental aerosol that has passed over central and eastern Europe and southern Russia. Reduction of the clear-sky UV index against the aerosol-free atmosphere was of 4.5%, 27% and 41% for the aerosol types 1, 2 and 3, respectively.

  8. Excellent microwave absorption property of Graphene-coated Fe nanocomposites

    PubMed Central

    Zhao, Xingchen; Zhang, Zhengming; Wang, Liaoyu; Xi, Kai; Cao, Qingqi; Wang, Dunhui; Yang, Yi; Du, Youwei

    2013-01-01

    Graphene has evoked extensive interests for its abundant physical properties and potential applications. It is reported that the interfacial electronic interaction between metal and graphene would give rise to charge transfer and change the electronic properties of graphene, leading to some novel electrical and magnetic properties in metal-graphene heterostructure. In addition, large specific surface area, low density and high chemical stability make graphene act as an ideal coating material. Taking full advantage of the aforementioned features of graphene, we synthesized graphene-coated Fe nanocomposites for the first time and investigated their microwave absorption properties. Due to the charge transfer at Fe-graphene interface in Fe/G, the nanocomposites show distinct dielectric properties, which result in excellent microwave absorption performance in a wide frequency range. This work provides a novel approach for exploring high-performance microwave absorption material as well as expands the application field of graphene-based materials. PMID:24305606

  9. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties.

    PubMed

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-07-28

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from -9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies.

  10. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties

    PubMed Central

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-01-01

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from −9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies. PMID:27465689

  11. The saturable absorption and reverse saturable absorption properties of Cu doped zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Yao, Cheng-Bao; Wen, Xin; Li, Qiang-Hua; Yan, Xiao-Yan; Li, Jin; Zhang, Ke-Xin; Sun, Wen-Jun; Bai, Li-Na; Yang, Shou-Bin

    2017-03-01

    We present the structure and nonlinear absorption (NLA) properties of Cu-doped ZnO (CZO) films prepared by magnetron sputtering. The films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the CZO films can maintain a wurtzite structure. Furthermore, the open-aperture (OA) Z-scan measurements of the film were carried out by nanosecond laser pulse. A transition from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the excitation intensity increasing. With good excellent nonlinear optical coefficient, the samples were expected to be the potential applications in optical devices.

  12. Titan's aerosol optical properties with VIMS observations at the limb

    NASA Astrophysics Data System (ADS)

    Rannou, Pascal; Seignovert, Benoit; Le Mouelic, Stephane; Sotin, Christophe

    2016-06-01

    The study of Titan properties with remote sensing relies on a good knowledge of the atmosphere properties. The in-situ observations made by Huygens combined with recent advances in the definition of methane properties enable to model and interpret observations with a very good accuracy. Thanks to these progresses, we can analyze in this work the observations made at the limb of Titan in order to retrieve information on the haze properties as its vertical profiles but also the spectral behaviour between 0.88 and 5.2 µm. To study the haze layer and more generally the source of opacities in the stratosphere, we use some observation made at the limb of Titan by the VIMS instrument onboard Cassini. We used a model in spherical geometry and in single scattering, and we accounted for the multiple scattering with a parallel plane model that evaluate the multiple scattering source function at the plane of the limb. Our scope is to retrieve informations about the vertical distribution of the haze, its spectral properties, but also to obtain details about the shape of the methane windows to desantangle the role of the methane and of the aerosols. We started our study at the latitude of 55°N, with a image taken in 2006 with a relatively high spatial resolution (for VIMS). Our preliminary results shows the spectral properties of the aerosols are the same whatever the altitude. This is a consequence of the large scale mixing. From limb profile between 0.9 and 5.2 µm, we can probe the haze layer from about 500 km (at 0.9 µm) to the ground (at 5.2 µm). We find that the vertical profile of the haze layer shows three distinct scale heights with transitions around 250 km and 350 km. We also clearly a transition around 70-90 km that may be due to the top of a condensation layer.

  13. Relationship between aerosol oxidation level and hygroscopic properties of laboratory generated secondary organic aerosol (SOA) particles

    NASA Astrophysics Data System (ADS)

    Massoli, P.; Lambe, A. T.; Ahern, A. T.; Williams, L. R.; Ehn, M.; Mikkilä, J.; Canagaratna, M. R.; Brune, W. H.; Onasch, T. B.; Jayne, J. T.; Petäjä, T.; Kulmala, M.; Laaksonen, A.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R.

    2010-12-01

    Laboratory experiments investigated the relationship between oxidation level and hygroscopic properties of secondary organic aerosol (SOA) particles generated via OH radical oxidation in an aerosol flow reactor. The hygroscopic growth factor at 90% RH (HGF90%), the CCN activity ($\\kappa$ORG,CCN) and the level of oxidation (atomic O:C ratio) of the SOA particles were measured. Both HGF90% and $\\kappa$ORG,CCN increased with O:C; the HGF90% varied linearly with O:C, while $\\kappa$ORG,CCN mostly followed a nonlinear trend. An average HGF90% of 1.25 and $\\kappa$ORG,CCN of 0.19 were measured for O:C of 0.65, in agreement with results reported for ambient data. The $\\kappa$ORG values estimated from the HGF90% ($\\kappa$ORG,HGF) were 20 to 50% lower than paired $\\kappa$ORG,CCN values for all SOA particles except 1,3,5-trimethylbenzene (TMB), the least hygroscopic of the SOA systems. Within the limitations of instrumental capabilities, we show that differences in hygroscopic behavior among the investigated SOA systems may correspond to differences in elemental composition.

  14. View From a Megacity: Aerosol Light Absorption and Scattering at Four Sites in and Near Mexico City.

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, G.; Arnott, W. P.; Gaffney, J. S.; Marley, N. A.

    2006-12-01

    As part of the Megacity Impacts on Regional and Global Environments, MIRAGE-Mex deployment to Mexico City in the period of 30 days, March 2006, a suite of photoacoustic spectrometers (PAS) were installed to measure at ground level the light absorption and scattering by aerosols at four sites: an urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP), a suburban site at the Technological University of Tecamac, a rural site at "La Biznaga" ranch, and a site at the Paseo de Cortes (altitude 3,810 meters ASL) in the rural area above Amecameca in the State of Mexico, on the saddle between the volcanoes Popocatepetl and Iztaccihuatl. The IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions while the other sites provided characterization of the plume, mixed in with any local sources. The second and third sites are north of Mexico City, and the fourth site is south. The PAS used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Instruments at the second and third sites operate at 870 nm, and the one at the fourth site at 780 nm. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In the urban site the aerosol absorption coefficient typically varies between 40 and 250 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed. Comparisons with TSI nephelometer scattering and Aetholemeter absorption measurements at the T0 site will be presented. We will present a broad overview of the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the IMP site. Insight on the dynamical connections will be discussed.

  15. Measurement and Modeling of Vertically Resolved Aerosol Optical Properties and Radiative Fluxes Over the ARM SGP Site

    NASA Technical Reports Server (NTRS)

    Schmid, B.; Arnott, P.; Bucholtz, A.; Colarco, P.; Covert, D.; Eilers, J.; Elleman, R.; Ferrare, R.; Flagan, R.; Jonsson, H.

    2003-01-01

    In order to meet one of its goals - to relate observations of radiative fluxes and radiances to the atmospheric composition - the Department of Energy's Atmospheric Radiation Measurement (ARM) program has pursued measurements and modeling activities that attempt to determine how aerosols impact atmospheric radiative transfer, both directly and indirectly. However, significant discrepancies between aerosol properties measured in situ or remotely remain. One of the objectives of the Aerosol Intensive Operational Period (TOP) conducted by ARM in May 2003 at the ARM Southern Great Plains (SGP) site in north central Oklahoma was to examine and hopefully reduce these differences. The IOP involved airborne measurements from two airplanes over the heavily instrumented SGP site. We give an overview of airborne results obtained aboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. The Twin Otter performed 16 research flights over the SGP site. The aircraft carried instrumentation to perform in-situ measurements of aerosol absorption, scattering, extinction and particle size. This included such novel techniques as the photoacoustic and cavity ring-down methods for in-situ absorption (675 nm) and extinction (675 and 1550 nm) and a new multiwavelength, filter-based absorption photometer (467, 530, 660 nm). A newly developed instrument measured cloud condensation nucleus concentration (CCN) concentrations at two supersaturation levels. Aerosol optical depth and extinction (354-2139 nm) were measured with the NASA Ames Airborne Tracking 14-channel sunphotometer. Furthermore, up-and downwelling solar (broadband and spectral) and infrared radiation were measured using seven individual radiometers. Three up-looking radiometers werer mounted on a newly developed stabilized platform, keeping the instruments level up to aircraft pitch and roll angles of approximately 10(exp 0). This resulted in unprecedented continuous vertical profiles

  16. Microwave absorption properties of pyrolytic carbon nanofilm

    PubMed Central

    2013-01-01

    We analyzed the electromagnetic (EM) shielding effectiveness in the Ka band (26 to 37 GHz) of highly amorphous nanometrically thin pyrolytic carbon (PyC) films with lateral dimensions of 7.2 × 3.4 mm2, which consists of randomly oriented and intertwined graphene flakes with a typical size of a few nanometers. We discovered that the manufactured PyC films, whose thickness is thousand times less than the skin depth of conventional metals, provide a reasonably high EM attenuation. The latter is caused by absorption losses that can be as high as 38% to 20% in the microwave frequency range. Being semi-transparent in visible and infrared spectral ranges and highly conductive at room temperature, PyC films emerge as a promising material for manufacturing ultrathin microwave (e.g., Ka band) filters and shields. PMID:23388194

  17. Comparison of the aerosol optical properties and size distribution retrieved by sun photometer with in situ measurements at midlatitude

    NASA Astrophysics Data System (ADS)

    Chauvigné, Aurélien; Sellegri, Karine; Hervo, Maxime; Montoux, Nadège; Freville, Patrick; Goloub, Philippe

    2016-09-01

    Aerosols influence the Earth radiative budget through scattering and absorption of solar radiation. Several methods are used to investigate aerosol properties and thus quantify their direct and indirect impacts on climate. At the Puy de Dôme station, continuous high-altitude near-surface in situ measurements and low-altitude ground-based remote sensing atmospheric column measurements give the opportunity to compare the aerosol extinction measured with both methods over a 1-year period. To our knowledge, it is the first time that such a comparison is realised with continuous measurements of a high-altitude site during a long-term period. This comparison addresses to which extent near-surface in situ measurements are representative of the whole atmospheric column, the aerosol mixing layer (ML) or the free troposphere (FT). In particular, the impact of multi-aerosol layers events detected using lidar backscatter profiles is analysed. A good correlation between in situ aerosol extinction coefficient and aerosol optical depth (AOD) measured by the Aerosol Robotic Network (AERONET) sun photometer is observed with a correlation coefficient around 0.80, indicating that the in situ measurements station is representative of the overall atmospheric column. After filtering for multilayer cases and correcting for each layer optical contribution (ML and FT), the atmospheric structure seems to be the main factor influencing the comparison between the two measurement techniques. When the site lies in the ML, the in situ extinction represents 45 % of the sun photometer ML extinction while when the site lies within the FT, the in situ extinction is more than 2 times higher than the FT sun photometer extinction. Moreover, the assumption of a decreasing linear vertical aerosol profile in the whole atmosphere has been tested, significantly improving the instrumental agreement. Remote sensing retrievals of the aerosol particle size distributions (PSDs) from the sun photometer

  18. The SOA formation model combined with semiempirical quantum chemistry for predicting UV-Vis absorption of secondary organic aerosols.

    PubMed

    Zhong, Min; Jang, Myoseon; Oliferenko, Alexander; Pillai, Girinath G; Katritzky, Alan R

    2012-07-07

    A new model for predicting the UV-visible absorption spectra of secondary organic aerosols (SOA) has been developed. The model consists of two primary parts: a SOA formation model and a semiempirical quantum chemistry method. The mass of SOA is predicted using the PHRCSOA (Partitioning Heterogeneous Reaction Consortium Secondary Organic Aerosol) model developed by Cao and Jang [Environ. Sci. Technol., 2010, 44, 727]. The chemical composition is estimated using a combination of the kinetic model (MCM) and the PHRCSOA model. The absorption spectrum is obtained by taking the sum of the spectrum of each SOA product calculated using a semiempirical NDDO (Neglect of Diatomic Differential Overlap)-based method. SOA was generated from the photochemical reaction of toluene or α-pinene at different NO(x) levels (low NO(x): 24-26 ppm, middle NO(x): 49 ppb, high NO(x): 104-105 ppb) using a 2 m(3) indoor Teflon film chamber. The model simulation reasonably agrees with the measured absorption spectra of α-pinene SOA but underestimates toluene SOA under high and middle NO(x) conditions. The absorption spectrum of toluene SOA is moderately enhanced with increasing NO(x) concentrations, while that of α-pinene SOA is not affected. Both measured and calculated UV-visible spectra show that the light absorption of toluene SOA is much stronger than that of α-pinene SOA.

  19. Radiative forcing of climate in the western Antarctic Peninsula: Effects of cloud, surface, and aerosol properties

    NASA Astrophysics Data System (ADS)

    Payton, Allison Mccomiskey

    2003-12-01

    Polar regions are expected to show early and extreme responses to a rise in average global temperatures. The region west of the Antarctic Peninsula has shown a significant rise in temperature of the past half century while temperatures over the rest of the continent are decreasing. Approximately half of the warming over the western Antarctic Peninsula has been explained by changes in atmospheric circulation. This research has examined local climate feedback processes involving aerosols, clouds, and surface properties relative to sea ice cover, to explain the remainder of the warming, and addresses the most appropriate approach in examining local radiative processes. Two data sets are used: a highly resolved ground-based data set from the spring and summer season of 1999 2000 at Palmer Station, Antarctica and a 14 year satellite-derived data set. A three- dimensional radiative transfer model is shown to perform better than the plane-parallel models traditionally used for this application. Aerosol concentrations are low, as expected, and have a typical optical depth of 0.05 which has little effect on surface radiation budgets and climate feedback processes. An absorption process is found on three clear-sky days that accounts for 5 20 W·m-2 of energy absorbed by the atmosphere. The absorption process is of unknown origin. Cloud properties over the short- and long-term were found to be invariant with time and changes in temperature except in the summer season. Cloud radiative forcing was negative throughout the 14 year time period, but the majority of this effect was attributed to changes in surface properties (decreasing reflectance) rather than increasing cloud amount or thickness. The trend in cloud cover over the long-term and the effect of clouds on climate appears to be different in the region of the western Antarctic Peninsula than in the Arctic.

  20. Nitrogen dioxide and kerosene-flame soot calibration of photoacoustic instruments for measurement of light absorption by aerosols

    SciTech Connect

    Arnott, W. Patrick; Moosmu''ller, Hans; Walker, John W.

    2000-12-01

    A nitrogen dioxide calibration method is developed to evaluate the theoretical calibration for a photoacoustic instrument used to measure light